An interview study of persons diagnosed with multiple myeloma between 1977 and 1981 and suitable control subjects was conducted to test the hypothesis that exposure to hair dyes increases the risk of multiple myeloma. Among women, there was little evidence that prior regular use of hair dyes (odds ratio [OR] = 1.0; 95% confidence interval [CI] = 0.70, 1.4) or prior employment as a hairdresser (OR = 1.1; 95% CI = 0.43, 2.7) increased risk; however, the former comparison was limited by the lack of detailed information concerning the exposure. Among men, there was a modest association of regular use of hair dyes (OR = 1.5; 95% CI = 0.75, 2.9) with myeloma, but this was based on a small number of exposed persons.