Cancer incidence was investigated in a cohort of 700 workers employed at a Connecticut chemical plant between mid-1965 and 1989. The plant produced a variety of chemicals, including arylamines such as dichlorobenzidine (DCB), o-dianisidine, o-tolidine, but not benzidine. Benzidine production ceased prior to mid-1965. The principal finding was a statistically significant increase in the standardized incidence ratio (SIR) for bladder cancer in men (SIR = 8.3; confidence interval, 3.3 to 17.0). Based on an exposure classification system developed by a panel of former and current employees, the observed association between bladder cancer cases and exposure to arylamines increased with increasing exposure (SIRs = 0.0, 5.5, 16.4, for none, low, or moderate levels of exposure, respectively). Smoking probably contributed to the bladder cancer risk, as all case subjects were known to be current or former cigarette smokers.