To investigate the clinical validity and utility of tests for detecting Epidermal Growth Factor Receptor (EGFR) gene mutations in non-squamous non-small cell lung cancer patients, tumour DNA extracts from 532 patients previously tested by the cobas EGFR Mutation Test (RT-PCR test) were retested by the Sequenom/Agena Biosciences MassArray OncoFocus mass spectrometry test (MS test). The gene discussed is EGFR; the disease is neoplasm.