Cancer incidence was assessed in 4,161 end-stage renal disease (ESRD) patients on dialysis to determine whether there was any excess risk of cancer in this population. Records from the Michigan Kidney Registry (MKR) for 1973 to 1984 were linked to those of the Michigan Cancer Foundation's Metropolitan Detroit Cancer Surveillance System (MDCSS) to identify cases in the dialysis cohort. The expected number of cancers in the ESRD population was calculated using the race-, sex-, age- and calendar year-specific incidence rates of the tricounty metropolitan Detroit region of 4 million residents. The standardized incidence ratio (observed:expected) was significantly increased for all in situ tumors combined, as well as for invasive tumors of the kidney, the corpus uteri, and the prostate. The four-fold to five-fold excess (P less than 0.005) observed for renal and endometrial cancers, in addition to the significantly elevated (P less than 0.05) risk of prostate cancer indicates that patients maintained on dialysis should be evaluated for these tumors when they experience even minor symptoms. Population-based cancer and renal disease registries provide excellent opportunities for investigating etiologic hypotheses and future studies should incorporate potential risk factors when analyzing these data.