This thesis is composed of two separate essays. In the first essay of this thesis, I examine data from the Voluntary Counseling and Testing Study Group's randomised controlled trial in which individuals learn their HIV status at different points in time. Aspects of sexual behavior were reported in surveys collected at an initial baseline as well as at a six month follow-up for all individuals I consider. These individuals were also tested for Sexually Transmitted Diseases (STDs) to determine if they were newly-infected. The interesting feature of the data that I look at is individuals who believed they were likely HIV negative but were actually HIV positive contracted more new STDs than individuals in a control group with similar beliefs and the same HIV status but who did not learn their status at baseline. This is despite not reporting riskier sexual behavior. Those who believed they were HIV positive but learned they were actually HIV negative contracted fewer new STDs than those in the comparable subgroup. In the second essay of this thesis, I develop a model which assumes truthful reporting that explains the varied STD contraction rates described in the first essay. The key feature of this model is that it allows for individuals to choose to meet a partner in one of two locations, producing a sorting equilibrium. Since there has been a question as to whether these individuals are truthfully reporting their behavior I also develop models that consider cases where individuals under-report their behavior. I show that even in this case a sorting equilibrium performs better when compared to the data, which implies that subsidizing HIV testing is a policy that reduces prevalence under the assumptions in that model.