Gallium nitrate is a group IIIa metal that was found to be active in animal species. Gallium nitrate exerts its antitumor effects via a transferrin binding mechanism. This agent is of interest in small cell lung cancer since 26 of 27 small cell carcinoma cell lines tested had increased levels of transferrin receptors. In a phase I study using a continuous infusion, the dose limiting toxicity was nausea when gallium nitrate was given at doses of 400 mg/m2/day. Other effects included elevations of serum creatinine, hypocalcemia, hypomagnesemia, decreased hearing and paresthesias. Activity has been seen in pretreated patients with malignant lymphoma, bladder carcinoma and small numbers of patients with small cell lung carcinoma. To determine the activity of continuous infusion gallium nitrate, this phase II trial was undertaken in patients with small cell lung cancer previously treated with chemotherapy.