Epidermal growth factor receptor (EGFR) signal blocking is an important goal for targeted therapy strategies in two ways: competitive inhibition of EGF binding by an antibody or of the receptor tyrosine kinase by small molecules.Recently, ligand-independent EGFR activating mutations were identified in non-small cell lung cancer (NSCLC).Two hotspot mutations located in exon 19 and exon 21 account for about 90% of all EGFR mutations.We designed a Bi-PASA (bidirectional PCR amplification of specific alleles) assay to detect the most common exon 19 deletion (codons 746-750) and an allele-specific PCR for the L858R mutation in exon 21.To validate the assays for use in clinical diagnostics, 35 lung adenocarcinoma samples were analyzed.Both assays provided the predicted amplification pattern for normal and mutant genotypes with high specificity and sensitivity.In serial dilution experiments, the mutant alleles were detectable in mixed samples with an at least 6-fold excess of normal DNA.Three exon 19 deletions were identified in the tumor samples.Both assays are fast and easy to perform in any routine PCR laboratory with no special equipment other than thermocyclers.The eosteffective test identifying ligand-independent EGFR activation, selected 3 out of 35 NSCLC patients who had maximal benefit from receptor tyrosine kinase inhibition and were prevented from side effects of an antibody-based therapy.