Somatostatin receptors of human gastrointestinal cancer specimens and cell lines were measured using in vitro film autoradiography. Four colon and one gastric cancer cell lines when grown as xenografts were receptor-positive. Of the 31 human colorectal cancers, forty percent were receptor-positive, and there was an association between advanced stage and poorer differentiation with receptor status. Biopsy specimens of two gastric, one pancreatic and one esophageal cancers were negative for somatostatin receptors.