A criterion for eligibility to compensation is sought for bladder cancer cases among workers in the aluminum smelting industry. Probability that a case of bladder cancer was caused by occupational exposure can be estimated from a relationship derived from results of epidemiologic studies. Because the effects of occupational exposure and smoking apparently combine multiplicatively, this probability is independent of whether a case patient smoked. Estimated probabilities of causation have been used in a criterion for eligibility to compensation by the Quebec workers' compensation board. Workers with cancer for whom the upper 95% confidence limit of the probability of causation is at least 50% are compensated. This implies a minimum cumulative exposure to benzo[a]pyrene (concentration in micrograms per cubic meter times duration in years) of 19 micrograms/m3 years. Possible alternative approaches to compensation are discussed.