WinNT 4 SP6a, all of the latest patches (yea, yea I know). PHP 4.3.1 I am getting 1,2,4, or more process instances of PHP running using 100% CPU. Cannot narrow it down to bad programming code by users or a php.exe problem. Most PHP is running fine. I have a few PHP forums running. I cannot reproduce the problem, but it is increasing. Concerned that it may be a attack. This is now occurring 4 or more times a day. Only option is to kill the errant processes. Sometimes a reboot of the server is mandatory. After killing the processes, normal PHP code in our forums runs fine. There are not any consistent instances of PHP runing in the background unless this problem reoccurs. The PHP.INI is set as follows; max_execution_tim = 30; max_imput_time = 60; memory_limit = 8M . It has now effect on this problem, we have seen it run over 4 hours without a sign of stopping on its own. I don't have the memory usage noted, there is not any unusually high traffic across our network during the instance. Most dynamic pages fail, only static pages are served from IIS, due to the high CPU load. PHP request run, but very slowly as do all request during this time.