Index: src/main/java/hudson/plugins/active_directory/ActiveDirectoryUnixAuthenticationProvider.java
===================================================================
--- src/main/java/hudson/plugins/active_directory/ActiveDirectoryUnixAuthenticationProvider.java	(revision 19032)
+++ src/main/java/hudson/plugins/active_directory/ActiveDirectoryUnixAuthenticationProvider.java	(working copy)
@@ -40,10 +40,10 @@
 public class ActiveDirectoryUnixAuthenticationProvider extends AbstractUserDetailsAuthenticationProvider
     implements UserDetailsService, GroupDetailsService {
 
-    private final String domainName;
+    private final String[] domainNames;
 
     public ActiveDirectoryUnixAuthenticationProvider(String domainName) {
-        this.domainName = domainName;
+        this.domainNames = domainName.split(",");
     }
 
     /**
@@ -61,6 +61,26 @@
     }
 
     protected UserDetails retrieveUser(String username, UsernamePasswordAuthenticationToken authentication) throws AuthenticationException {
+        UserDetails userDetails = null;
+        for (String domainName : domainNames) {
+            try {
+                userDetails = retrieveUser(username, authentication, domainName);
+            }
+            catch (BadCredentialsException bce) {
+                LOGGER.log(Level.WARNING,"Credential exception tying to authenticate against " + domainName + " domain",bce);
+            }
+            if (userDetails != null) {
+                break;
+            }
+        }
+        if (userDetails == null) {
+            LOGGER.log(Level.WARNING,"Exhausted all configured domains and could not authenticat against any.");
+            throw new BadCredentialsException("Either no such user '"+username+"' or incorrect password");
+        }
+        return userDetails;
+    }
+    
+    private UserDetails retrieveUser(String username, UsernamePasswordAuthenticationToken authentication, String domainName) throws AuthenticationException {
         String password = null;
         if(authentication!=null)
             password = (String) authentication.getCredentials();
@@ -90,8 +110,9 @@
                 // failed to find it. Fall back to sAMAccountName.
                 // see http://www.nabble.com/Re%3A-Hudson-AD-plug-in-td21428668.html
                 renum = context.search(toDC(domainName),"(& (sAMAccountName="+username+")(objectClass=user))", controls);
-                if(!renum.hasMore())
+                if(!renum.hasMore()) {
                     throw new BadCredentialsException("Authentication was successful but cannot locate the user information for "+username);
+                }
             }
             SearchResult result = renum.next();
 
Index: src/main/java/hudson/plugins/active_directory/ActiveDirectorySecurityRealm.java
===================================================================
--- src/main/java/hudson/plugins/active_directory/ActiveDirectorySecurityRealm.java	(revision 19032)
+++ src/main/java/hudson/plugins/active_directory/ActiveDirectorySecurityRealm.java	(working copy)
@@ -86,50 +86,54 @@
         public void doDomainCheck(StaplerRequest req, StaplerResponse rsp, @QueryParameter("value") final String value) throws IOException, ServletException {
             new FormFieldValidator(req,rsp,true) {
                 protected void check() throws IOException, ServletException {
-                    String name = Util.fixEmptyAndTrim(value);
-                    if(name==null) {// no value given yet
+                    String n = Util.fixEmptyAndTrim(value);
+                    if(n==null) {// no value given yet
                         ok();
                         return;
                     }
-                    if(!name.endsWith(".")) name+='.';
+                    
+                    String[] names = n.split(",");
+                    for (String name : names) {
+                    
+                        if(!name.endsWith(".")) name+='.';
 
-                    DirContext ictx;
+                        DirContext ictx;
 
-                    // first test the sanity of the domain name itself
-                    try {
-                        LOGGER.fine("Attempting to resolve "+name+" to A record");
-                        ictx = createDNSLookupContext();
-                        Attributes attributes = ictx.getAttributes(name, new String[]{"A"});
-                        Attribute a = attributes.get("A");
-                        if(a==null) throw new NamingException();
-                        LOGGER.fine(name+" resolved to "+ a.get());
-                    } catch (NamingException e) {
-                        LOGGER.log(Level.WARNING,"Failed to resolve "+name+" to A record",e);
-                        error(name+" doesn't look like a valid domain name");
-                        return;
-                    }
+                        // first test the sanity of the domain name itself
+                        try {
+                            LOGGER.fine("Attempting to resolve "+name+" to A record");
+                            ictx = createDNSLookupContext();
+                            Attributes attributes = ictx.getAttributes(name, new String[]{"A"});
+                            Attribute a = attributes.get("A");
+                            if(a==null) throw new NamingException();
+                            LOGGER.fine(name+" resolved to "+ a.get());
+                        } catch (NamingException e) {
+                            LOGGER.log(Level.WARNING,"Failed to resolve "+name+" to A record",e);
+                            error(name+" doesn't look like a valid domain name");
+                            return;
+                        }
 
-                    // then look for the LDAP server
-                    final String ldapServer = "_ldap._tcp."+name;
-                    String serverHostName;
-                    try {
-                        serverHostName = obtainLDAPServer(ictx,name);
-                    } catch (NamingException e) {
-                        LOGGER.log(Level.WARNING,"Failed to resolve "+ldapServer+" to SRV record",e);
-                        error("No LDAP server was found in "+name);
-                        return;
-                    }
+                        // then look for the LDAP server
+                        final String ldapServer = "_ldap._tcp."+name;
+                        String serverHostName;
+                        try {
+                            serverHostName = obtainLDAPServer(ictx,name);
+                        } catch (NamingException e) {
+                            LOGGER.log(Level.WARNING,"Failed to resolve "+ldapServer+" to SRV record",e);
+                            error("No LDAP server was found in "+name);
+                            return;
+                        }
 
-                    // try to connect to LDAP port to make sure this machine has LDAP service
-                    // TODO: honor the port number in SRV record
-                    try {
-                        new Socket(serverHostName,389).close();
-                    } catch (IOException e) {
-                        LOGGER.log(Level.WARNING,"Failed to connect to LDAP port",e);
-                        error("Failed to connect to the LDAP port (389) of "+serverHostName);
-                        return;
+                        // try to connect to LDAP port to make sure this machine has LDAP service
+                        // TODO: honor the port number in SRV record
+                        try {
+                            new Socket(serverHostName,389).close();
+                        } catch (IOException e) {
+                            LOGGER.log(Level.WARNING,"Failed to connect to LDAP port",e);
+                            error("Failed to connect to the LDAP port (389) of "+serverHostName);
+                            return;
+                        }
                     }
-
                     // looks good
                     ok();
                 }
Index: src/main/webapp/help/domain-name-windows.html
===================================================================
--- src/main/webapp/help/domain-name-windows.html	(revision 19032)
+++ src/main/webapp/help/domain-name-windows.html	(working copy)
@@ -1,5 +1,5 @@
 <div>
-  Optionally specify the Active Directory domain name to authenticate against.
+  Optionally specify the Active Directory domain(s) name to authenticate against.
 
   <p>
   By default, Hudson uses <a  href="http://msdn.microsoft.com/en-us/library/aa772170.aspx">ADSI</a>
@@ -10,4 +10,6 @@
   that's running Hudson is not a domain user (which is the case if you install Hudson as a service,
   for example.) In such a case, please specify the domain name explicitly here, and Hudson uses
   standard LDAP protocol to talk to Active Directory.
+  <p>
+  It is also possible to specify multiple domains by separating them with a comma.
 </div>
\ No newline at end of file
Index: src/main/webapp/help/domain-name-unix.html
===================================================================
--- src/main/webapp/help/domain-name-unix.html	(revision 19032)
+++ src/main/webapp/help/domain-name-unix.html	(working copy)
@@ -1,4 +1,5 @@
 <div>
-    Specify the full domain name of Active Directory. Hudson uses this information to locate the LDAP service
-    and performs authentication.
+    Specify the full domain name(s) of Active Directory. Hudson uses this information to locate the LDAP service
+    and performs authentication. If you wish to attempt authentication against multiple Active Directory domains 
+    the entries can be sepparated by a comma.
 </div>
\ No newline at end of file