A total of 270 bladder cancer cases, 178 first-degree relatives and 127 spouses of the bladder cancer cases and 329 hospital controls were studied to evaluate the association between palmar keratoses, bladder cancer and environmental and genetic factors. Crude prevalences of keratoses in the 4 groups were 67, 54, 42 and 23%, respectively. Logistic regression models showed that bladder cancer patients had a raised risk of having palmar keratoses relative to hospital controls (odds ratio = 6.95; 95% CI: 4.77-10.12) whereas blood-relatives and spouses had significantly increased odds ratios only if the case in their family (or some other blood-relative) possessed keratoses. Among several environmental and behaviour factors, only cigarette smoking was significantly associated with increased risk (odds ratio = 2.32; 95% CI: 1.63-3.29). The data suggest a genetic component may influence the occurrence of palmar keratoses, but some unknown environmental agent appears to be causing the association between spouses.