A method, apparatus, system, and signal-bearing medium that, in an embodiment, determine the classes that are needed during a first invocation of an application and preload those classes during a subsequent invocation of the application. In various embodiments, the classes may be preloaded if they are within a specified package, if they were needed greater than a threshold number of times, if the class path did not change between the first invocation and the subsequent invocation, or if the jar files the contain the classes are in a class path. In this way, an embodiment of the invention may increase the performance of class preloading.