Detection of mutations in EGFR exons 18-21 is of particular clinical interest as these alterations can modulate response to EGFR inhibitors in lung adenocarcinoma patients (2,3) . Figures 3F, G and H depict the application of s-RT-MELT for screening DNA from lung cancer cell lines that harbor dHPLC-identified alterations in EGFR exons 19-21, including a two-codon deletion (del L747-E749, exon 19). The ability of s-RT-MELT for detecting low-level EGFR mutations was evaluated by performing DNA dilutions of a heterozygous EGFR exon 20 into a homozygous sample. A 1-10% mutant-to-wildtype ratio was detectable in this dilution experiment ( Figure 3F) . Finally, the application of s-RT-MELT in detecting mutations in DNA from formalin-fixed paraffinembedded (FFPE) samples was examined by screening four clinical FFPE lung adenocarcinoma specimens. Two of these samples were known to harbor EGFR exon 21 mutations (L858R), while the other two were negative for mutations when independently evaluated via dHPLC (28) . Figure 3I demonstrates the identification of the mutational status of these samples via s-PCR-MELT.