BACKGROUND: We evaluated the cost-effectiveness of the WINGS project, an intervention to prevent HIV and other sexually transmitted diseases among urban women at high risk for sexual acquisition of HIV. METHODS: We used standard methods of cost-effectiveness analysis. We conducted a retrospective analysis of the intervention's cost and we used a simplified model of HIV transmission to estimate the number of HIV infections averted by the intervention. We calculated cost-effectiveness ratios for the complete intervention and for the condom use skills component of the intervention. RESULTS: Under base case assumptions, the intervention prevented an estimated 0.2195 new cases of HIV at a cost of 215,690percaseofHIVaverted.WhenindirectcostsofHIVwereexcludedfromtheanalysis,theintervention′scost−effectivenessratioswere357,690 per case of HIV averted and 31,851perquality−adjustedlifeyear(QALY)saved.Underbasecaseassumptions,thecondomuseskillscomponentoftheinterventionpreventedanestimated0.1756HIVinfectionsandwascost−saving.WhenindirectHIVcostswereexcluded,thecost−effectivenessratiosforthecondomuseskillscomponentoftheinterventionwere97,404 per case of HIV averted and $8,674 per QALY saved. CONCLUSIONS: The WINGS intervention, particularly the two sessions of the intervention which focussed on condom use skills, could be cost-effective in preventing HIV among women