As a result of the current STI epidemic, women are at particularly high risk. Sexual relations with men are the greatest source of risk for women in contracting HIV or other STIs. Because the male condom is still the most effective means of protection against these diseases, prevention efforts for women need to concentrate on the ability to effectively negotiate condom use. To date, research has primarily addressed the role of knowledge, attitudes, and beliefs about condoms in predicting their use rather than the situation within which individuals make sexual decisions. Our first goal is to present a theoretical model focusing on the situational influences and cognitive processes occurring at the time of a woman's sexual interaction with a man. The underlying premise for this model is that sexual decision making is mediated by a series of primary and secondary appraisals during the sexual encounter. Our second goal is to discuss specific contextual influences on women's cognitions during the process leading to sexual decision making. We review the literature on the effects of alcohol consumption, relationship status, and sexual arousal on the cognitive appraisal process, as well as on sexual decision making. Finally, although our main interest is the specific situation and context, we also review the influence of background factors and experiences that are especially relevant to the cognitive appraisal process, including alcohol expectancies, sexual victimization, sexuality-related characteristics, relationship-related characteristics, and other personality traits. Examining women's cognitive processes at the time of a sexual encounter can yield information that will enhance women's power to protect themselves against HIV and other STIs.