We evaluated octreotide scintigraphy in 81 untreated patients who were suspected of having bronchial carcinoma. Octreotide scintigraphy visualized the primary tumour in all of 40 patients with non-small-cell lung carcinoma (non-SCLC), and all of 26 patients with SCLC. In the remaining patients, other bronchial disease and metastases from extrapulmonary carcinomas were also visualized. Mediastinal lymph node involvement and distant metastases were recognized in 5 of 15 and 1 of 7 patients with non-SCLC, respectively. In vitro, none of the non-SCLCs were shown to bear somatostatin receptors. We postulate that the visualization of non-SCLC during octreotide scintigraphy is caused by binding of labelled octreotide to activated leucocytes or to proliferating neuroendocrine cells around the tumours. In patients with SCLC, radiologically suspected lymph node involvement was visualized for 21 of 25 sites. Distant metastases, especially to the liver and abdomen, were missed for 14 of 20 sites, most probably because no laxatives were administered and single photon emission tomography of the abdomen was not performed. The failure to recognize liver metastases is most probably due to a comparable uptake of radioactivity by the surrounding normal liver tissue. In 15 of 26 patients, previously unrecognized tumour sites were suggested during octreotide scintigraphy, leading to a downstaging of 5 of 14 patients with limited disease. Unexpected cerebral metastases were suggested in five patients with either limited or extensive disease. In all four of these for whom follow-up was available, cerebral metastases became manifest 5-8 months after octreotide scintigraphy.(ABSTRACT TRUNCATED AT 250 WORDS)