Using the Swedish Cancer-Environment Register, 424,127 cancer patients were followed in the national cause-of-death register with the aim of analyzing the suicide rate among cancer patients compared with the general population. The overall Standardized Mortality Ratio (SMR) in suicide was 1.9 (95% confidence interval 1.8-2.1) for males and 1.6 (1.5-1.8) for females. The suicide rate was highest during the first year after cancer diagnosis, with an SMR of 16.0 (13.5-18.9) in males and 15.4 (11.2-20.6) in females. There were no substantial differences in suicide rate between different sites of tumor, although higher suicide rates were observed in patients with cancer in the lungs and upper airways (both sexes) and with gastro-intestinal tumors (males). Our results corroborate previous findings of an increased suicide rate among cancer patients, and indicate a need for further attention to social and psychological aspects of the care and treatment of cancer patients.