Abnormalities of chromosome 1, including trisomy for all or a portion of the long arm, have been frequently reported in many cancers. Anomalies of chromosome 19 are far less common, although a t(1;19)(q23;p13) translocation has been reported in association with pre-B-cell leukemia. We have observed a t(1;19)(q12;p13) translocation in three cases of advanced melanoma, with the translocation chromosome representing an extra dose of 1q in each instance. The breakpoint on 1q was within the centromeric heterochromatin, proximal to the site in pre-B-cell leukemia, but the breakpoint on 19p appeared identical. The gene for human insulin receptor has recently been mapped to this region of chromosome 19 (p13.2-13.3). This gene shares structural and sequence homologies with the epidermal growth factor receptor (erb-B oncogene) and members of the src family of oncogenes, suggesting that alterations in the insulin receptor, resulting from chromosomal translocation, could lead to a role in tumorigenesis. The present findings may permit this possibility to be examined in a neoplasm of neuroectodermal origin.