The human c-erbA1 gene has been previously mapped to chromosome 17. We have now mapped c-erbA2 to the short arm of chromosome 3, using a human genomic probe in Southern analysis of DNA from a panel of human/mouse somatic cell hybrids. In situ hybridization using the same probe on metaphase chromosomes has enabled fine chromosome mapping of c-erbA2 to the chromosome region 3p21-pter.