Granulomatous diseases can be visualized in vivo after the injection of indium-111-DTPA-octreotide (111In-pentetreotide), a radiolabelled somatostatin analogue. We evaluated whether somatostatin receptor imaging reflects disease activity, whether certain scintigraphic characteristics can predict the disease prognosis and whether repeat scintigraphy correlates with the clinical course in patients with sarcoidosis. 111In-pentetreotide was injected in 46 patients and images were obtained 24 h later. Known mediastinal, hilar and interstitial disease was recognized in 36 of 37 patients. Also, such pathology was found in seven other patients who had normal chest X-rays. In five of these, somatostatin receptor imaging pointed to interstitial disease. Frequently, accumulation of radioactivity in parotid glands and supraclavicular lymph nodes was found. Neither the degree of radioactive accumulation in the thorax nor a specific pattern of pathological uptake was correlated with disease severity or clinical course. The degree of uptake of radioactivity in the parotid glands was correlated with significantly higher serum angiotensin-converting enzyme (ACE) levels. Somatostatin receptor imaging was repeated in 13 patients. In five of six patients in whom chest X-ray monitored improvement of disease activity, the pentetreotide scintigram also showed a decrease in pathological uptake. In two of five patients in whom the chest X-ray was unchanged, but serum ACE concentrations had decreased and lung function improved, normalization on pentetreotide scintigrams was found. It is concluded that: (1) somatostatin receptor imaging can demonstrate active granulomatous disease in patients with sarcoidosis; (2) pathological uptake of radioactivity in the parotid glands during somatostatin receptor imaging is correlated with higher serum ACE concentrations; (3) the value of somatostatin receptor imaging in the follow-up of patients with sarcoidosis will have to be determined in a prospective longitudinal study.