Small-cell lung carcinoma (SCLC) is characterized by a consensus deletion in the short arm of chromosome 3. Using a panel of cell lines and somatic cell hybrids containing various rearrangements involving chromosome 3, we have localized the erbA beta sequence (which codes for a thyroid hormone receptor) to the region 3p21----3p25 which overlaps the consensus deletion in SCLC. Moreover, we have shown by Southern blot analysis that at least one copy of the erbA beta sequence is deleted in all six SCLCs so far studied. Normalized ratios of hybridization intensities of the erbA beta probe to intensities of probes for somatostatin (3q28) and raf(3p24-25) ranged from 0.28 to 0.56 and 0.32 to 0.71, respectively, in the six tumors and tumor lines. In view of the importance of the role these genes are known or suspected to play in biological regulation, our results suggest that the erbA beta sequence is a candidate for a recessive oncogene involved in the genesis of SCLC.