Gout patients might be at an increased risk of cancer because of obesity and heavy alcohol drinking, but uric acid has antioxidant properties, which may protect against carcinogenesis. We compared the incidence of cancer among 16 857 gout patients admitted to hospitals in Sweden during 1965-1995 with that of the national population. A total of 1425 malignant neoplasms were diagnosed in gout patients (standardized incidence ratio 1.25, 95% confidence limits 1.18, 1.31). The incidence of cancers of the oral cavity and pharynx, colon, liver and biliary tract, pancreas, lung, skin (melanoma and nonmelanoma), endometrium and kidney, as well as of malignant melanoma was increased among gout patients. With the exception of lung cancer, the risk remained elevated during the entire follow-up. This study provides no evidence of a protective effect of uric acid. Hyperuricemia may be an early manifestation of the carcinogenic process.