Genetic alterations of the genes encoding protein kinases have been implicated in the development of human cancers. Myosin light chain kinase 2, skeletal muscle (MYLK2) encodes a calcium/calmodulin-dependent serine/threonine kinase. In a recent study, MYLK2 gene was somatically mutated in colorectal carcinomas. The aim of this study was to explore the possibility that other common human carcinomas besides colorectal carcinomas harbored MYLK2 mutations in the kinase domain. We analyzed exons 6 and 7 eccoding the kinase domain of MYLK2 for somatic mutations in 60 gastric, 104 colorectal, 79 non-small cell lung, and 54 breast cancers using a polymerase chain reaction (PCR)-based single-strand conformation polymorphism (SSCP). We found one MYLK2 mutation in lung adenocarcinomas, but not in other cancers. The MYLK2 mutation detected was a missense mutation that would substitute an amino acid (E374D) However, there was no somatic mutation of the MYLK2 gene. These data suggest that the kinase domain of MYLK2 is rarely mutated in common human carcinomas and that it does not play a dominant role in cancer pathogenesis.