If you detect that the thread pool is the bottleneck and the cause is some lengthy Web service calls, then first you should try the asynchronous approaches discussed before. That will improve the performance of your app significantly. If that doesn’t address your issue, then you should switch to IIS 6.0 if you still use IIS 5.0 or increase the size of the thread pool by changing the setting of your machine.config. Most likely you have a very heavily loaded site and you should scale out other applications on the same machine where the Web server is located. So the change made on the machine.config file will not affect on other applications.