Objective. We explored links among economically motivated relationships, transactional sex, and risk behavior for human immunodeficiency virus (HIV) and sexually transmitted infections (STIs) among unmarried African American and white women. Methods. We drew on data from 1,371 unmarried African American and white women aged 20 to 45 years that we collected via a random-digit-dial telephone survey in the U.S. Results. Of all respondents, 33.3% (95% confidence interval 28.8, 38.0) reported staying in a relationship longer than they wanted to because of economic considerations. African American women were more likely than white women to report starting a relationship due to economic considerations (21.6% vs. 10.5%) and having transactional sex with someone who was not a regular partner (13.1% vs. 2.9%). These behaviors were all associated with lack of education, experience of economic hardship, need to care for dependents, and increased levels of HIV/STI risk. All three behaviors were associated with having more sexual partners. Staying in a sexual relationship because of economic considerations was also associated with anal sex, reduced condom use, and concurrent sexual partnerships. Transactional sex with non-regular partners was associated with concurrent sexual partnerships, binge drinking, drug use, perceived concurrency by main partner, and having high-risk sexual partners. Conclusion. HIV/STI risk-reduction policies and programs in the U.S. need to explicitly address overall economic disempowerment among women, as well as racial disparities in poverty. These economic disparities likely contribute both to increasing rates of HIV among women in the U.S. and to the extraordinary racial disparities in HIV/STI risk among American women.