To the Editor. —Padian et al1studied 379 heterosexual couples for evidence of human immunodeficiency virus (HIV) transmission and found that male-to-female transmission is much greater than female-to-male. In the single case of female-to-male transmission, the index case had multiple sexual contacts and reported vaginal bleeding during sex, and her regular male partner who seroconverted also reported penile bleeding during sex. Are the results of this study consistent with the results of other such studies? We reviewed the literature searching for HIV serologic studies of heterosexual couples with both male and female index cases.1-8Studies were excluded if only female-to-male or male-to-female transmission was studied. We started with all studies referenced in the Padian et al article and reviewed the abstracts of the Seventh International Conference on AIDS. We identified 16 studies meeting the study definition. The designs of the 16 studies were similar. Heterosexual individuals (index cases)