Occupational exposure to aromatic amines is a known bladder cancer risk factor, whereas the impact of exposure to azo dyes, which may release aromatic amines in humans, is at present controversial. Therefore, the impact of occupational exposures to colorants was investigated in 156 bladder cancer cases and 336 controls in the state of North Rhine-Westphalia. All bladder cancer cases and controls (diagnosed with prostate cancer) requested after-care treatment. The subjects were investigated using a questionnaire for all occupations ever performed for more than 6 mo and for exposures to several possible occupational and nonoccupational bladder carcinogens. The relative bladder cancer risk was adjusted for age and smoking. The adjusted odds ratio (OR) for bladder cancer was elevated in 7 painters (OR 1.98, 95% CI 0.64-6.11), 4 hairdressers (OR 4.9, 95% CI 0.85-28.39), and 16 cases who reported a wood processing occupation (OR 1.19, 95% CI 0.58-2.41). Ten of these 16 cases reported chronic exposure to colorants (OR 1.84, 95% CI 0.68-4.95). The results of this epidemiological study confirm the hypothesis that individuals exposed to colorants show an elevated bladder cancer risk.