GOUTY arthropathy, urate lithiasis, and acute uric acid nephropathy may all complicate the course in a patient who has a malignant disease. All three problems originate from an increased uric acid turnover that occurs in this type of disease. Hyperuricemia may range in importance from an incidental chemical abnormality to a life-threatening complication. Therefore, when it is encountered in this situation, it should not be ignored. Although hyper-uricemia is seen most commonly in association with acute and chronic leukemias, lymphomas, myeloma, and the myeloproliferative syndromes, it is also noted with increasing frequency in patients with nonhematologic malignancy. Often present before treatment, its prevalence and severity increase during successful radiotherapy or chemotherapy of the malignant disease. Increased production of uric acid is the by-product of unrestrained tumor-cell growth. As effective treatment destroys malignant cells, serum uric acid levels rise because of a limited renal capacity for handling urate. Elevated serum uric