A total of 6600 pregnant urban women attending an antenatal clinic of a major hospital in Malawi were evaluated for risk factors for human immunodeficiency virus type 1 (HIV-1) infection. HIV-1 seroprevalence was 23% and significantly (P < .001) associated with markers of heterosexual activity (history of sexually transmitted diseases [STDs], more than one sexual partner, reports of husbands with other partners, and all prevalent STDs except chlamydial infection) and higher socioeconomic status (as measured by husband's education). History of injections, scarification, and transfusions were not associated with HIV-1 infection. In two logistic regression models, higher socioeconomic status was a risk factor for HIV-1 infection (odds ratio [OR] = 2.69, P < .001) but not for STDs (OR = 0.94, P = .30). The opposite associations between HIV-1 and socioeconomic status and STDs and socioeconomic status suggest that HIV prevention strategies, in addition to STD diagnosis and treatment, should include interventions to reduce high-risk sexual activity and promote condom use.