A total of 13 patients with metastatic carcinoid tumour, paraganglioma, or unclassified "apudoma" were treated with single-agent carboplatin at a dose of 400 mg/m2 given by intravenous infusion every 4 weeks, on the basis that this new agent shows high activity against small-cell lung cancer that also has "apudoma" characteristics. No objective tumour responses were seen. Overall, 2 patients achieved minor regression, 4/9 (44%) showed a reduction of greater than 50% in urinary 5-HIAA excretion and 8/13 (62%) reported symptomatic improvement. Treatment was well tolerated, with neutropenia and thrombocytopenia being the main toxicities. Carboplatin, like other cytotoxic agents, does not appear to have major activity against these tumours, although further studies in patients with metastatic paraganglioma are warranted.