Receptor tyrosine kinase ALK is commonly activated either by fusions or mutations. ALK-fusions have been identified in anaplastic large-cell lymphoma, non-small cell lung cancer and inflammatory myofibroblastic tumors. Crizotinib, an ALK inhibitor, was recently approved for treatment of advanced metastatic lung cancers that express EML4-ALK fusion. However, patients often acquire resistance due to ALK kinase domain mutations. MolecularMD’s bi-directional Sanger sequencing assay identifies variation in ALK exons 22-25, including detection of the L1196M gatekeeper mutation.