In this paper we present a new compilation method based on program transformation. The principle is to separate the compilation of pattern matching from its optimization, and describe optimizations using transformation rules. This eases the compilation of extensions, such as new equational theories, or the addition of or-patterns for example. In addition, we show that the proposed optimizations are correct and effective in practice. The presented approach has been implemented and applied to Tom, a language extension which adds pattern-matching facilities to C and Java.