Earlier proportional mortality studies of workers in a plastics producing plant in Massachusetts indicated excess mortality from certain digestive and genitourinary cancers. To more definitively examine mortality among these workers a retrospective cohort study was conducted for 2,490 male wage earners who worked at least one year during 1949–1966. Vital status was determined as of Dec. 31, 1976, for 99.7% of the cohort and death certificates were obtained for 98.0% of 603 observed deaths. Comparison with the local county white males revealed a slight excess in digestive system cancer (standard mortality ratio [SMR] = 101.8] and a statistically significant excess (p<.05) in genitourinary cancer (SMR = 153.6). A relationship was suggested between cancer of the rectum, liver, and pancreas and both the duration and interval from onset of exposure. A secondary matched case-control study was conducted to determine if particular jobs or work areas were related to the excesses found in the primary study. This analysis did not support the hypothesis that digestive or genitourinary cancer was related to a general plant exposure or date of hire. Possible associations warranting continued surveillance were found between rectal cancer and cellulose nitrate production and between prostatic cancer and polystyrene processing. Digestive and genitourinary cancers other than rectal and prostate were not related to employment in any of 21 occupational exposure categories examined.