The incidence of ovarian cancer and non-Hodgkin's lymphomas (NHL) between 1971 and 1985 or 1987 has been studied on the basis of cancer registry data among women employed in hairdressing or related occupations at 1970 census in Denmark, Sweden, Norway, and Finland. Overall, the standardized incidence ratio (SIR) for ovarian cancer was 1.18 (95% confidence interval, 0.98 to 1.40). The increase was present among hairdressers from Denmark (SIR, 1.23) and Finland (SIR, 1.88); whereas hairdressers from Sweden and Norway had an incidence close to expectation (SIR 0.95 and 0.96, respectively). In three of the four countries, the SIR was higher in 1971 to 1975 than in later years. The SIR for NHL was 1.20 (0.84 to 1.66); an excess was seen in Denmark (SIR, 1.92) and a decrease was found in Sweden (SIR, 0.63). In previous studies, hairdressers have been reported to be at increased risk of ovarian cancer: this study adds some evidence in favor of the presence of an association. This study also offers some support to the hypothesis of an association between exposure to hair dyes and risk of NHL, that was reported among personal users from the United States. This study, however, strongly suggests that occupational cancer risk among female hairdressers depends on temporal and geographical factors.