Previous investigations of cancer among firefighters have been limited to mortality data and have yielded inconsistent results. Case-control analyses were conducted in the present surveillance study in order to examine associations between firefighting and cancer incidence in Massachusetts. Subjects were identified through the Massachusetts Cancer Registry files for 1982-1986. Exposure status (firefighting) was determined from the usual occupation reported to the Registry. Nine different cancer types were examined among the 315 reported white male firefighters. Two "unexposed" reference populations were used: policemen and statewide males. Standardized morbidity odds ratios (SMORs) were statistically significantly elevated for melanoma (SMOR = 292; 95% C.I. = 170-503) and bladder cancer (SMOR = 159; 95% C.I. = 102-250) among firefighters compared with the state as a whole. When policemen were used as the reference group, the bladder cancer excess persisted (SMOR = 211; 95% C.I. = 107-414) and non-Hodgkin's lymphoma was elevated (SMOR = 327; 95% C.I. = 119-898); the melanoma excess was largely reduced (SMOR = 138; 95% C.I. = 60-319) but remained elevated among those aged 55-74 years (SMOR = 513; 95% C.I. = 150-1,750). Small number excesses (not significant) were also observed for pancreatic cancer and leukemia compared with police.