We have examined a series of human colorectal adenomas, carcinomas and cell lines derived from human colorectal cancer for loss of heterozygosity (LOH) on chromosome 11q22-23 by polymerase chain reaction (PCR) amplification of a microsatellite polymorphism of the dopamine D2 receptor (DRD2) locus. The gene discussed is DRD2; the disease is colorectal cancer.