Small cell lung cancer is a common and aggressive disease. Combined multiagent chemotherapy and radiotherapy can improve short-term prognosis, but long-term prognosis remains dim. Somatostatin receptors have been identified on the cellular surface of subsets of this cancer and may be associated with less aggressive evolution. Moreover, medical therapy with somatostatin analogues holds promise for neoplastic growth control. Planar scintigraphy has been performed in 15 patients with histologically proven small cell lung cancer at 4 and 24 h after the intravenous (i.v.) injection of 185 MBq 111In-octreotide (Octreoscan, BYK-Gulden). No short-term adverse effects were recorded; tumour uptake of the radiopharmaceutical was observed in 13 patients at 4 h and in 12 patients at 24 h suggesting more extensive disease than apparent by computed tomography (CT). It is highly likely that the 24 h uptake reflects the presence of somatostatin receptors on the tumour. Previous chemotherapy does not seem to play a key role in tumour visualization. 111In-octreotide is a suitable radiopharmaceutical for in vivo evaluation of somatostatin receptor status of small cell lung cancer. Quantitative sdntigraphic methods are needed to investigate nonspecific binding and receptor kinetics.