The chapter details the methodology for polymerase chain reaction amplification and WAVE denaturing high-performance liquid chromatography (DHPLC) analysis for all coding exons for the gene PTPNI1, which is mutated in approx 50% of cases of Noonan Syndrome. Although DNA sequencing is initially required to determine the mutation(s) detected by WAVE (sequencing methods are not described in this chapter), each mutation has its own DHPLC signature, and experienced operatives can determine known mutations on this basis. The new Navigator software has made this process more reliable.