Consistent chromosomal translocations in neoplastic cells may alter the expression of proto-oncogenes that are located near the breakpoints. The complementary DNA sequence of the human insulin receptor is similar to those of the EGF receptor (erbB oncogene) and products of the src family of oncogenes. With in situ hybridization and Southern blot analysis of somatic cell hybrid DNA, the human insulin receptor gene was mapped to the distal short arm of chromosome 19 (bands p13.2----p13.3), a site involved in a nonrandom translocation in pre-B-cell acute leukemia.