FLEX is a compiler infrastructure written in Java for Java. Applications include a program analysis and transformation framework for distributed and embedded systems. Native backends exist for the StrongARM and MIPS processors; it can also generate portable C code that can run on any platform with gcc. It supports both Boehm-Demers-Weiser conservative garbage collection and our own precise garbage collector. We also support region-based allocation via our implementation of the Real-Time Specification for Java. It fully supports several implementations of the standard Java threads package, including a standard heavyweight threads implementation as well as a lightweight user-level implementation. It provides a range of standard compiler analyses and optimizations, as well as unique optimizations for embedded targets, including space optimization.