diff --git a/ChangeLog b/ChangeLog
index 2d27d199..c99c97e7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -9,6 +9,12 @@
     Type: feature
     Changed: linkchecker
 
+  * Allow infinite recursion in CGI script, and add a warning about
+    performance requirements.
+    Type: feature
+    Changed: cgi-bin/lconline/lc_cgi.html.*, linkcheck/lc_cgi.py,
+      doc/en/install.txt
+
 4.2 "V for Vendetta" (released 26.7.2006)
 
   * Drop privileges when running as root under Unix systems. Add
diff --git a/cgi-bin/lconline/lc_cgi.html.de b/cgi-bin/lconline/lc_cgi.html.de
index 116ee737..68a3e4aa 100644
--- a/cgi-bin/lconline/lc_cgi.html.de
+++ b/cgi-bin/lconline/lc_cgi.html.de
@@ -55,6 +55,7 @@ target="_top">LinkChecker</a>)
   <option value="1" selected>1</option>
   <option value="2">2</option>
   <option value="3">3</option>
+  <option value="-1">unendlich</option>
   </select>
 </td>
 <td>Prüfe Anker in HTML:</td>
diff --git a/cgi-bin/lconline/lc_cgi.html.en b/cgi-bin/lconline/lc_cgi.html.en
index 525124c1..1f60288a 100644
--- a/cgi-bin/lconline/lc_cgi.html.en
+++ b/cgi-bin/lconline/lc_cgi.html.en
@@ -48,6 +48,7 @@ target="_top">LinkChecker</a>)
   <option value="1" selected>1</option>
   <option value="2">2</option>
   <option value="3">3</option>
+  <option value="-1">infinite</option>
   </select>
 </td>
 <td>Check anchors in HTML:</td>
diff --git a/doc/en/install.txt b/doc/en/install.txt
index 96bbbdca..2774a812 100644
--- a/doc/en/install.txt
+++ b/doc/en/install.txt
@@ -175,6 +175,11 @@ interface.
 You can use and adjust the example HTML files in the lconline directory
 to run the script.
 
+0. Note that running LinkChecker requires CPU and memory resources.
+   Allowing a CGI script to execute such a program for possibly a
+   large number of users might deplete those resources.
+   Be sure to only allow access from trusted sites to this script.
+   
 1. Choose a CGI script. The simplest is lc.cgi and you need a web server
    with CGI support.
    The script lc.fcgi (I tested this a while ago) needs a web server
diff --git a/linkcheck/lc_cgi.py b/linkcheck/lc_cgi.py
index 0f963da3..4b8b95b8 100644
--- a/linkcheck/lc_cgi.py
+++ b/linkcheck/lc_cgi.py
@@ -35,7 +35,7 @@ import linkcheck.director
 
 _logfile = None
 _supported_langs = ('de', 'fr', 'nl', 'C')
-_is_level = re.compile(r'^[0123]$').match
+_is_level = re.compile(r'^(0|1|2|3|-1)$').match
 
 class FormError (StandardError):
     """