Although patients with type 2 diabetes have elevated risks of liver, pancreatic, kidney, and endometrial cancer, little is known about the risk of cancer for patients with type 1 diabetes. We conducted a cohort study to examine cancer incidence among 29 187 patients in Sweden who were hospitalized for type 1 diabetes from 1965 through 1999. Relative risks of cancer were estimated by age-, sex- and calendar year of follow-up–adjusted standardized incidence ratios (SIRs), using data for the entire Swedish population as a reference. After excluding cancers diagnosed during the first year after hospital discharge, we observed 355 incident cases of cancer, which corresponded to a 20% increase in overall cancer incidence among type 1 diabetes patients (SIR = 1.2, 95% confidence interval [CI] = 1.0 to 1.3). Patients with type 1 diabetes had elevated risks of cancers of the stomach (SIR = 2.3, 95% CI = 1.1 to 4.1), cervix (SIR = 1.6, 95% CI = 1.1 to 2.2), and endometrium (SIR = 2.7, 95% CI = 1.4 to 4.7). Type 1 diabetes is associated with a modest excess cancer risk overall and risks of specific cancers that differ from those associated with type 2 diabetes.