There are two genes related to the v-erb B oncogene in the human genome. The c-erb B-1 gene encodes the epidermal growth factor receptor (EGF-r), and the c-erb B-2/neu gene encodes a receptor-like protein very similar to, but distinct from the EGF-r. Southern blot analysis of DNAs from 15 fresh human ovarian carcinomas showed that the c-erb B-2/neu gene was amplified in 3 tumors. The c-erb B-1/EGF-r gene was not amplified. However, in one case of adenocarcinoma of uterine endometrium, the c-erb B-1/EGF-r was found to be rearranged in the 5' region of this gene. The genomic structure of the rearranged c-erb B-1/EGF-r gene is similar to those found in the chicken v-erb B oncogene, which produces a truncated form of the EGF-r. The results suggest that amplification of the c-erb B-2/neu gene may play a role in the pathogenesis of ovarian carcinoma. Further, the human c-erb B-1/EGF-r gene in adenocarcinoma of uterine endometrium may be activated by a similar mechanism as that in the chicken v-erb B oncogene.