Matched normal/tumor DNA pairs from patients with sporadic and hereditary (FAP = familial adenomatous polyposis) colorectal carcinoma were examined for tumor-specific allele loss on chromosome 6 using cDNA probes for the avian myeloblastosis viral oncogene homologue (MYB on 6q22-q23), the estrogen receptor (ESR on 6q24-q27), and for the alpha polypeptide of human chorionic gonadotropin (CGA on 6q14-q21). No chromosome 6 allele loss was observed at these gene loci among 22 colorectal carcinomas examined, although such losses were relatively frequent (37.5% of informative individuals) at the D17S28 locus on chromosome 17. These results are consistent with karyological studies and indicate that chromosome 6 allele loss from colorectal carcinomas may occur less frequently than previously reported.