Recently, natural and social scientists have pointed out that the need to make scientific results apply to both sexes is not met by simply adding women as research subjects. They suggest that the social and biological specificity of both sexes must be recognized and adjustments made to the ways questions are asked, hypotheses are generated, research subjects are chosen, and data are analysed. It is important to examine the definitions, concepts and methods used in research in occupational health to see whether they obstruct recognition of women's occupational health problems or interfere with gender-neutral standard setting. Unravelling the effects of sex on occupational health is complicated by the fact that women and men do not, by and large, work at the same jobs. Definitions of "work" must in some cases be adjusted to take account of women's occupations, just as definitions involving "health" must include women's biological specificity. Appropriate changes must be made to generate sex-inclusive definitions of exposures to occupational hazards and of health effects. Methods for evaluating exposures typical of women's work must be developed. Women and their work must be appropriately included when standards for occupational exposures are set. If these adjustments are not made, women's occupational health problems will be seriously underestimated and understanding of health problems of both sexes will be hindered. Sociological analysis should also be done to reveal the mechanisms by which biased concepts and procedures develop and are reinforced.