This study has assessed gender differences in smoking and the use of smokeless tobacco for younger adults and their parents in samples from five ethnic groups in Kenya. These samples were from two groups of pastoralists (the Maasai and the Samburu), a group engaged in fishing and farming (the Luo), and two groups of relatively Westernized Kenyans primarily involved in commercial occupations (from the Kisii and the Gikuyu ethnic groups). In four of the five study groups, there was little or no difference in the prevalence of smokeless tobacco use in either the younger or older generation. Similarly, in four of the study groups there was little or no gender difference in the prevalence of smoking for the older generation. In contrast, for the younger generation in every study group except the Luo, men were much more likely than women to smoke cigarettes. The attitudes toward tobacco use reported by the younger generation showed similar patterns. In every study group except the Luo, the younger adults reported that smokeless tobacco use was socially acceptable for both men and women, but smoking was acceptable only for men. Many of the younger women reported that they did not smoke because it would not be socially acceptable. The interview data suggest that the social prohibition against women's smoking was one component of more general restrictions on women's behavior, and the absence of restrictions on men's smoking was related to men's greater social power. The Luo were the only study group in which respondents reported that women should have as much influence as men in decision making. Correspondingly, the Luo were the only study group in which most respondents considered it acceptable for women to smoke and women were as likely as men to smoke cigarettes.