The met oncogene was previously isolated from a chemically transformed human cell line, MNNG-HOS. Recent evidence has demonstrated that two classes of transcripts are expressed from the met proto-oncogene locus. The met oncogene, however, expresses an aberrant RNA which has sequences in common with both transcripts. We now report partial nucleotide sequencing of the human met oncogene and show that met is related to the protein kinase oncogenes and growth factor receptors. The met nucleotide sequence is not identical to that of any published gene, and it is more closely homologous to the tyrosine kinases than to the serine/threonine kinases. Within the tyrosine kinase family, the sequenced met domains are most closely related to the human insulin receptor and the viral abl gene. In situ chromosome hybridization has mapped met to human chromosome 7 band 7q21-q31, a location distinct from that of other kinases. This is also a region associated with nonrandom chromosomal deletions observed in a portion of patients with acute nonlymphocytic leukaemia. The accompanying paper shows that this chromosomal locus is also tightly linked with the human heredity disease cystic fibrosis.