This multi-site randomized, controlled trial will measure the effectiveness of the diaphragm in preventing heterosexual acquisition of HIV infection among women. This Phase III study is powered to detect effectiveness (biological efficacy combined with adherence) of 33 percent. Women in South Africa and Zimbabwe (N=4,500) at risk of contracting HIV will be invited to participate and will be followed for up to 24 months, with a total study duration of 4 years. All women will receive safer-sex counseling, free male condoms and diagnosis and treatment of sexually transmitted infections (STIs). Half of the participants will be randomly selected to receive an Ortho All-Flex latex diaphragm and Replens lubricant gel. We will assess whether women using diaphragms and lubricant gel have lower rates of HIV or STI infection than do their non-diaphragm and gel counterparts. Additionally, we will investigate the long-term acceptability of the diaphragm in this study population.