Gender power inequities are believed to play a key role in the HIV epidemic through their effects on women's power in sexual relationships. We hypothesized that lack of sexual power, measured with a four-point relationship control scale and by a woman's experience of forced sex with her most recent partner, would decrease the likelihood of consistent condom use and increase the risk for HIV infection among sexually experienced, 15- to 24-year-old women in South Africa. While limited sexual power was not directly associated with HIV, it was associated with inconsistent condom use: women with low relationship control were 2.10 times more likely to use condoms inconsistently (95% confidence interval [CI] 1.17-3.78), and women experiencing forced sex were 5.77 times more likely to use condoms inconsistently (95% CI 1.86-17.91). Inconsistent condom use was, in turn, significantly associated with HIV infection (adjusted odds ratio 1.58, 95% CI 1.10-2.27).