[snip] Hi there, I do work on following regex: ^(.*)_a[0-9](.*).htm$ This should be valid for "test_a9393.htm", but not for "9393.htm" as ther is no leading _a infront of the number. Unfortunatelly this also works for the 9393.htm file. Can somebody give me a hint why the regex also is true for text that does not start with _a infront of the number? Thank you for any help, Merlin [/snip] How about this: (\w)+(_a){1}(\w)+\.htm$ Worked for me :) HTH Dan -- Dan Parry Senior Developer Virtua Webtech Ltd http://www.virtuawebtech.co.uk -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.394 / Virus Database: 268.8.0/352 - Release Date: 30/05/2006 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php