PURPOSE: To explore agreement on cancer occurrence and site among Medicare Part A, Massachusetts Cancer Registry, and death certificates. METHODS: We linked these data sources with the cohort of the population based East Boston Senior Health Project, a component of the National Institute on Aging's Established Populations for Epidemiologic Studies of the Elderly. The cohort consists of 905 subjects dying between January 1986 and December 1990. RESULTS: We detected the following agreements on cancer occurrence: hospitalization data and death certificates (kappa = 0.70), hospitalization and cancer registry data (kappa = 0.59), and cancer registry and death certificate data (kappa = 0.50). Measures of agreement changed little when the analyses were stratified by age, sex, calendar year and place of death, autopsy performance, cigarette smoking or alcohol consumption. Site-specific agreements were higher for colorectal and respiratory tract cancer compared to breast and prostate across ail three comparisons. CONCLUSIONS: The results should assist epidemiologists to better understand the strengths and limitations of these data sources. (C) 1998 Elsevier Science Inc.