diff --git a/EcAlerter.h b/EcAlerter.h
index 4801448..f0c11d3 100644
--- a/EcAlerter.h
+++ b/EcAlerter.h
@@ -116,6 +116,17 @@
  *   them to a nice readable version, and also match a default rule to
  *   log full details to the technical team.</em>
  *   </desc>
+ *   <term>Tag</term>
+ *   <desc>Specifies a tag to be associated with this event during execution
+ *   of any subsequent rules (until/unless the event is re-tagged).<br />
+ *   The tag actually associated with the event is obtained by treating
+ *   the tag value as a template and substituting in any values (as for
+ *   the Replace and Rewrite fields).
+ *   </desc>
+ *   <term>Tagged</term>
+ *   <desc>The message is matched if (and only if) it has been tagged
+ *   with a value exactly equal to the value of this field.
+ *   </desc>
  *   <term>Flush</term>
  *   <desc>A boolean (YES or NO) saying whether stored messages due to
  *   be sent out later should be sent out immediately after processing
diff --git a/EcAlerter.m b/EcAlerter.m
index 0c88b4c..ca14cbb 100644
--- a/EcAlerter.m
+++ b/EcAlerter.m
@@ -478,6 +478,13 @@ replaceFields(NSDictionary *fields, NSString *template)
           RELEASE(pool);
           pool = [NSAutoreleasePool new];
           d = [rules objectAtIndex: i];
+
+          s = [d objectForKey: @"Tagged"];
+          if (s != nil && NO == [s isEqual: [m objectForKey: @"Tag"]])
+            {
+              continue;         // Not a match.
+            }
+
           s = [d objectForKey: @"Type"];
           if (s != nil && [s isEqualToString: type] == NO)
             {
@@ -573,10 +580,15 @@ replaceFields(NSDictionary *fields, NSString *template)
               [m setObject: s forKey: @"Message"];
             }
 
-          /* Remove any old Replacement setting ... will set up specifically
-           * for the output alert type later.
+          /* Set the tag for this event if necessary ... done *after*
+           * all matching, but before sending out the alerts.
            */
-          [m removeObjectForKey: @"Replacement"];
+          if (nil != [d objectForKey: @"Tag"])
+            {
+              NSString  *s = replaceFields(m, [d objectForKey: @"Tag"]);
+
+              [m setObject: s forKey: @"Tag"];
+            }
 
           NS_DURING
             {
@@ -614,6 +626,7 @@ replaceFields(NSDictionary *fields, NSString *template)
                 localException);
             }
           NS_ENDHANDLER
+          [m removeObjectForKey: @"Replacement"];
 
           NS_DURING
             {
@@ -659,6 +672,7 @@ replaceFields(NSDictionary *fields, NSString *template)
                 localException);
             }
           NS_ENDHANDLER
+          [m removeObjectForKey: @"Replacement"];
 
           NS_DURING
             {
@@ -731,6 +745,7 @@ replaceFields(NSDictionary *fields, NSString *template)
                 localException);
             }
           NS_ENDHANDLER
+          [m removeObjectForKey: @"Replacement"];
           [m removeObjectForKey: @"EmailIdentifier"];
           [m removeObjectForKey: @"EmailInReplyTo"];
 
@@ -772,6 +787,7 @@ replaceFields(NSDictionary *fields, NSString *template)
                 localException);
             }
           NS_ENDHANDLER
+          [m removeObjectForKey: @"Replacement"];
 
           s = [d objectForKey: @"Flush"];
           if (s != nil)