S_mary Human colorectal cancer tissue and matched uninvolved mucosa from 21 patients were examined by radioligand displacement for the presence of binding sites for bombesin-like peptides. Five cancers, but no univolved mucosa, expressed high-affinity, low-capacity bombesin binding sites (KYd = 6.53 nM, B.. = 58.6 fmol mg-' protein) of the gastrin-releasing peptide (GRP)-preferring subtype (IC50 4.8 nM).Bombesin-like peptides may have a role in the pathogenesis of colorectal cancer, and bombesin receptor antagonists may be of value in the treatment of receptor-positive tumours.