One of the topics we often get questions on is about when it makes sense to invest the extra effort to pre-compile assemblies via NGen instead of simply relying on the JIT compiler to generate native code on the fly at application runtime. I thought I would try to answer that question in our first "real" post. The JIT is optimized to balance code generation time against code quality, and it works well for many scenarios. NGen is essentially a performance optimization; so just like for anything else that's performance-related, you'll want to measure performance with vs. without NGen, and then decide whether it really helps your specific application and scenario. Here are a few general guidelines.