This paper describes an experimental system in which customized high performance XML parsers are prepared using parser generation and compilation techniques. Parsing is integrated with Schema-based validation and deserialization, and the resulting validating processors are shown to be as fast as or in many cases significantly faster than traditional nonvalidating parsers. High performance is achieved by integration across layers of software that are traditionally separate, by avoiding unnecessary data copying and transformation, and by careful attention to detail in the generated code. The effect of API design on XML performance is also briefly discussed. Categories and Subject Descriptors D.3.4 [Programming Languages]: Processors ? code generation, compilers, optimization, parsing, retargetable compilers. D.2.8 [Software Engineering]: Metrics ? Performance measures. I.7.2 [XML] General Terms Performance, Experimentation, Standardization, Languages. Keywords XML, XML Schema, performan...