Six patients (4 women, 2 men) with malignant gastrinoma developed multiple bone metastases; osteolytic as well as osteoblastic lesions occurred. All lesions involved the central skeleton, most caused symptoms, and, in 2 cases, there was associated hypercalcemia with normal serum parathormone levels. Poor responses were observed after treatment with cytotoxic drugs, but good symptomatic responses occurred after radiotherapy in 2 of the 4 patients in whom it was used. The peptic ulcer component of the disease was well controlled in all patients by cimetidine with or without anticholinergic supplements or by ranitidine alone in doses of 300-600 mg daily. Five of the 6 patients died with a mean survival after diagnosis of Zollinger-Ellison syndrome of 3.3 yr (range 1.0-7.0 yr), suggesting that bone metastases are associated with a poor prognosis in metastatic gastrinoma.