I have built an iPhone app with SDK 4.2 however I know also want to make it compatible with iOS 3.1.3. First step was to set the Deployment Target to 3.1.3. It runs fine on the 3.2 Simulator but the app crashes at times since I'm using some methods which are not available in this early SDK. So my qestion is, is there a straight forward way to locate the offending methods/classes I'm using in my project which are not available in 3.1.3 ? (without manually going through each method call and consult with the docs for the SDK availability?) Thanks. UPDATE: I have executed the app on 3.1.3 and attempted to manually test each execution path with the hope of locating all exceptions. This was completed with some level of success. However, what if the application is huge? and there are lots of execution paths? There must be some tool for this scenario. Any thoughts are much appreciated.