Many countries are not on track to meet the UNAIDS target of ending HIV as a public health threat by 2030. One manner in which progress towards such targets to reduce new HIV infection can be accelerated is through improved use of HIV prevention methods. The HIV Prevention Cascade framework can be used as a way of identifying the levels of primary prevention method use and barriers to use among adolescent girls and young women - a target group for increasing HIV prevention method use - and their potential male partners. The overarching aim of this thesis was to use the HIV prevention cascade framework to measure levels of prevention method use, as well as barriers to prevention method use among adolescent girls and young women and their male partners. Analysis of risk factors associated with HIV acquisition identified some sexual risk behaviours consistently associated with acquisition of HIV infection, including selfreporting a non-regular or concurrent sexual partners. Evaluation of a risk differentiation tool to predict combined HIV/HSV-2 acquisition gave good sensitivity among those already sexually active and reporting a non-regular partner was predictive of HIV/HSV-2 acquisition. However, rapid change in sexual risk behaviour was observed across 12 months of follow up and over half of new infections occurred in those not reporting to have started sex at baseline. Validation of the HIV prevention cascade framework demonstrated that it was feasible to populate the HIV prevention cascade framework, including both the main and sub bars, using data collected as part of the Manicaland Pilot HIV Prevention Cascades Study. Analysis using the HIV prevention cascade framework found that male condoms were the most commonly used prevention method and PrEP was the least. Barriers to prevention method use were identified using the HIV prevention cascade framework, which indicate potential targets for interventions to improve prevention method use. Barriers were identified for all prevention methods and at each step of the prevention cascade, indicating the need for multi-level interventions which target individual, provider, community and structural factors.