A substantial body of risk research indicates that women and men differ in their perceptions of risk. This paper discusses how they differ and why. A review of a number of existing empirical studies of risk perception points at several problems, regarding what gender differences are found in such studies, and how these differences are accounted for. Firstly, quantitative approaches, which have so far dominated risk research, and qualitative approaches give different, sometimes even contradictory images of women's and men's perceptions of risk. Secondly, the gender differences that appear are often left unexplained, and even when explanations are suggested, these are seldom related to gender research and gender theory in any systematic way. This paper argues that a coherent, theoretically informed gender perspective on risk is needed to improve the understanding of women's and men's risk perceptions. An analysis of social theories of gender points out some relations and distinctions which should be considered in such a perspective. It is argued that gender structures, reflected in gendered ideology and gendered practice, give rise to systematic gender differences in the perception of risk. These gender differences may be of different kinds, and their investigation requires the use of qualitative as well as quantitative methods. In conclusion, the arguments about gender and risk perception are brought together in a theoretical model which might serve as a starting point for further research.