The author reviews cross-cultural studies correlating women's reproductive functions with states of ritual defilement, pollution, and cultural restrictions on social behavior. Women's reproductive functions--childbirth, menstruation, and sexual intercourse--are frequently viewed as contaminating. Thus, during her menstrual period or period surrounding childbirth, a woman may be isolated to protect others, especially men, from sickness, injury, or loss of sexual potency. To date, anthropological studies of feminine pollution have produced some significant statistical correlations and a number of different and unrelated theoretical interpretations. In the first part of the paper, the author deals with theories pertaining to feminine pollution. Studies are discussed in which the extent of menstrual taboos has been found to correlate with social variables such as degree of male dominance, male solidarity, and social rigidity. It has also been correlated with certain customs affecting childhood socialization, notably the duration of the postpartum sex taboo. The second part of the paper discusses cross-cultural interpretations of menstrual taboos. Theoretical explanations of the existence and intensity of menstrual taboos and other forms of female pollution have used various ecological, social, and psychological facts as independent or mediating variables. In the final part of the paper, the author synthesizes the findings of various authors within a single theoretical framework. She suggests the following hypothesis: women will be seen as polluting to the degree that a culture assigns formal social power to men and women possess informal social power within the domestic unit. Women's informal social power can be illustrated by the post-partum sex taboo which increases the amount of time a mother spends with her children, thereby increasing their dependence on her and her social influence over them. This social power in societies formally dominated by men makes women anomalous, and therefore men fear them as polluting. (Author/AV)