I agree with what other people have said that it really depends on the application, the programmer, the db and hardware. I think if you could make an exactly equivalent app in ASPX and PHP, and run it on exactly equivalent hardware, then the ASPX would actually run faster, just because it's compiled. I'll say that ASPX sites tend to be more complex, and because of that there's more the programmer can do wrong that will make it run slower. There's part of your answer. I'll also say that one really common reason that ASPX sites run slowly is out-of-control viewstates. Something like a forum that uses a repeater could have viewstate info for every control shown on the page, and that viewstate has to get transferred over the wire in both directions. So it's just the extra bandwidth making it seem slow. (I have actually coded pages with >200KB viewstates. My bad...)