The SHC gene encodes a protein that is thought to act as an adapter in many signal transduction pathways; the SHC protein probably facilitates the activation of RAS proteins in response to a variety of factors. We have mapped the human SHC gene and have identified a new SHC-related sequence. We have sequenced the region corresponding to the SHC 3' UTR from both loci and have mapped cosmids by fluorescence in situ hybridization. The human SHC gene maps to the proximal long arm of chromosome 1 and the SHC-related sequence maps to the proximal long arm of chromosome 17. A number of cancers have been positioned in the proximal long arm of chromosome 1; this is of interest given the oncogenic potential of the SHC protein.