OBJECTIVE: Diabetes is the sixth leading cause of death in U.S adults, which may be an underestimate because of under-reporting on death certificates. In this study we examined death certificate sensitivity and specificity for diabetes, as well as the factors related to better reporting, in a community-based sample. RESEARCH DESIGN AND METHODS: Death certificates were obtained for 3,209 decedents who were enrolled in the Rancho Bernardo cohort in 1972-1974 and followed through 2003. Diabetes status was reassessed at periodic clinic visits and annual mailed surveys during an average follow-up of 15.2 +/- 7.6 years. Diabetes reported anywhere on death certificates was abstracted. Sensitivity and specificity calculations among diabetic participants were stratified by age, sex, year, place, cause of death, and diabetes medication use. RESULTS: Among 1,641 men and 1,568 women, 378 decedents had a history of diabetes, 168 of whom had diabetes listed anywhere on their death certificates. The sensitivity and specificity were 34.7 and 98.1%. Diabetes reporting on death certificates did not improve over time or vary significantly by age and sex, but sensitivity for diabetes reporting was better for recent (1992-2003) cardiovascular disease (CVD) deaths compared with any other causes of death (48.9 vs. 28.6%, respectively, P < 0.05). CONCLUSIONS: Although diabetes reporting on death certificates did not improve over time, sensitivity was better for diabetes in the context of CVD deaths, probably reflecting the increasing recognition that diabetes is a major cardiovascular risk factor.