diff --git a/NewsStats.pm b/NewsStats.pm
index 35e0c90..2cb1be2 100644
--- a/NewsStats.pm
+++ b/NewsStats.pm
@@ -31,6 +31,7 @@ require Exporter;
   SplitPeriod
   ListMonth
   ListNewsgroups
+  ReadGroupList
   OutputData
   FormatOutput
   SQLHierarchies
@@ -154,15 +155,23 @@ sub ListNewsgroups {
 ### explode a (scalar) list of newsgroup names to a list of newsgroup and
 ### hierarchy names where every newsgroup and hierarchy appears only once:
 ### de.alt.test,de.alt.admin -> de.ALL, de.alt.ALL, de.alt.test, de.alt.admin
-### IN : $Newsgroups: a list of newsgroups (content of Newsgroups: header)
-### OUT: %Newsgroups: hash containing all newsgroup and hierarchy names as keys
-  my ($Newsgroups) = @_;
+### IN : $Newsgroups  : a list of newsgroups (content of Newsgroups: header)
+###      $ValidGroupsR: reference to a hash containing all valid newsgroups
+###                     as keys
+### OUT: %Newsgroups  : hash containing all newsgroup and hierarchy names as keys
+  my ($Newsgroups,$ValidGroupsR) = @_;
+  my %ValidGroups = %{$ValidGroupsR} if $ValidGroupsR;
   my %Newsgroups;
   chomp($Newsgroups);
   # remove whitespace from contents of Newsgroups:
   $Newsgroups =~ s/\s//;
   # call &HierarchyCount for each newsgroup in $Newsgroups:
   for (split /,/, $Newsgroups) {
+    # don't count invalid newsgroups
+    if(%ValidGroups and !defined($ValidGroups{$_})) {
+      warn (sprintf("DROPPED: %s\n",$_));
+      next;
+    }
     # add original newsgroup to %Newsgroups
     $Newsgroups{$_} = 1;
     # add all hierarchy elements to %Newsgroups, amended by '.ALL',
@@ -194,6 +203,26 @@ sub ParseHierarchies {
   return @Hierarchies;
 };
 
+################################################################################
+sub ReadGroupList {
+################################################################################
+### read a list of valid newsgroups from file (each group on one line,
+### ignoring everything after the first whitespace and so accepting files
+### in checkgroups format as well as (parts of) an INN active file)
+### IN : $Filename    : file to read
+### OUT: \%ValidGroups: hash containing all valid newsgroups
+  my ($Filename) = @_;
+  my %ValidGroups;
+  open (my $LIST,"<$Filename") or die "$MySelf: E: Cannot read $Filename: $!\n";
+  while (<$LIST>) {
+    s/^(\S+).*$/$1/;
+    chomp;
+    $ValidGroups{$_} = '1';
+  };
+  close $LIST;
+  return \%ValidGroups;
+};
+
 ################################################################################
 
 #####----------------------------- TimePeriods ----------------------------#####
diff --git a/gatherstats.pl b/gatherstats.pl
index 26b71e5..a721b3e 100755
--- a/gatherstats.pl
+++ b/gatherstats.pl
@@ -19,7 +19,7 @@ BEGIN {
 }
 use strict;
 
-use NewsStats qw(:DEFAULT :TimePeriods ListNewsgroups);
+use NewsStats qw(:DEFAULT :TimePeriods ListNewsgroups ReadGroupList);
 
 use DBI;
 
@@ -33,7 +33,7 @@ my %LegalTypes;
 ################################# Main program #################################
 
 ### read commandline options
-my %Options = &ReadOptions('dom:p:t:n:r:g:c:s:');
+my %Options = &ReadOptions('dom:p:t:l:n:r:g:c:s:');
 
 ### read configuration
 my %Conf = %{ReadConfig('newsstats.conf')};
@@ -54,6 +54,9 @@ die "$MySelf: E: Unknown type '-t $Options{'t'}'!\n" if !exists($LegalTypes{$Opt
 ### get time period (-m or -p)
 my ($StartMonth,$EndMonth) = &GetTimePeriod($Options{'m'},$Options{'p'});
 
+### read newsgroups list from -l
+my %ValidGroups = %{&ReadGroupList($Options{'l'})} if $Options{'l'};
+
 ### init database
 my $DBHandle = InitDB(\%Conf,1);
 
@@ -72,18 +75,25 @@ foreach my $Month (&ListMonth($StartMonth,$EndMonth)) {
 
     # count postings per group
     my %Postings;
-
     while (($_) = $DBQuery->fetchrow_array) {
       # get list oft newsgroups and hierarchies from Newsgroups:
-      my %Newsgroups = ListNewsgroups($_);
+      my %Newsgroups = ListNewsgroups($_,$Options{'l'} ? \%ValidGroups : '');
       # count each newsgroup and hierarchy once
       foreach (sort keys %Newsgroups) {
-        # don't count newsgroup/hierarchy in wrong TLH
-        next if(defined($Conf{'TLH'}) and !/^$Conf{'TLH'}/);
         $Postings{$_}++;
       };
     };
 
+    # add valid but empty groups if -l is set
+    if (%ValidGroups) {
+      foreach (sort keys %ValidGroups) {
+        if (!defined($Postings{$_})) {
+          $Postings{$_} = 0 ;
+          warn (sprintf("ADDED: %s as empty group\n",$_));
+        }
+      };
+    };
+
     print "----- GroupStats -----\n" if $Options{'d'};
     foreach my $Newsgroup (sort keys %Postings) {
       print "$Newsgroup => $Postings{$Newsgroup}\n" if $Options{'d'};
@@ -112,7 +122,7 @@ gatherstats - process statistical data from a raw source
 
 =head1 SYNOPSIS
 
-B<gatherstats> [B<-Vhdo>] [B<-m> I<YYYY-MM>] [B<-p> I<YYYY-MM:YYYY-MM>] [B<-t> I<type>] [B<-n> I<TLH>] [B<-r> I<database table>] [B<-g> I<database table>] [B<-c> I<database table>] [B<-s> I<database table>]
+B<gatherstats> [B<-Vhdo>] [B<-m> I<YYYY-MM>] [B<-p> I<YYYY-MM:YYYY-MM>] [B<-t> I<type>] [B<-l> I<filename>] [B<-n> I<TLH>] [B<-r> I<database table>] [B<-g> I<database table>] [B<-c> I<database table>] [B<-s> I<database table>]
 
 =head1 REQUIREMENTS
 
@@ -219,6 +229,17 @@ Set processing type to one of I<all> and I<groups>. Defaults to all
 (and is currently rather pointless as only I<groups> has been
 implemented).
 
+=item B<-l> I<filename> (check against list)
+
+Check each group against a list of valid newsgroups read from
+I<filename>, one group on each line and ignoring everything after the
+first whitespace (so you can use a file in checkgroups format or (part
+of) your INN active file).
+
+Newsgroups not found in I<filename> will be dropped (and logged to
+STDERR), and newsgroups found in I<filename> but having no postings
+will be added with a count of 0 (and logged to STDERR).
+
 =item B<-n> I<TLH> (newsgroup hierarchy)
 
 Override I<TLH> from F<newsstats.conf>.
@@ -259,9 +280,10 @@ Process all types of information for January of 2010:
 
     gatherstats -m 2010-01
 
-Process only number of postings for the year of 2010:
+Process only number of postings for the year of 2010,
+checking against checkgroups-2010.txt:
 
-    gatherstats -p 2010-01:2010-12 -t groups
+    gatherstats -p 2010-01:2010-12 -t groups -l checkgroups-2010.txt
 
 =head1 FILES