As new female-initiated HIV prevention products enter development, it is crucial to incorporate women's preferences to ensure products will be desired, accepted, and used. A discrete-choice experiment was designed to assess the relative importance of six attributes to stated choice of a vaginally delivered HIV prevention product. Sexually active women in South Africa and Zimbabwe aged 18-30 were recruited from two samples: product-experienced women from a randomized trial of four vaginal placebo forms and product-naïve community members. In a tablet-administered survey, 395 women chose between two hypothetical products over eight choice sets. Efficacy was the most important, but there were identifiable preferences among other attributes. Women preferred a product that also prevented pregnancy and caused some wetness (p < 0.001). They disliked a daily-use product (p = 0.002) and insertion by finger (p = 0.002). Although efficacy drove preference, wetness, pregnancy prevention, and dosing regimen were influential to stated choice of a product, and women were willing to trade some level of efficacy to have other more desired attributes.