This study will investigate what factors may lead to the development of immune reconstitution syndrome (IRIS) in HIV-infected patients and what the outcome is after IRIS. It will also seek to better define and describe the syndrome. IRIS is a condition that can occur in HIV-infected people following the start of antiretroviral therapy. The sudden improvement of immune function with this therapy can cause an unexpected worsening of diseases the patient already has, such as tuberculosis or fungal infections, and development of fever, enlarged lymph nodes or other complications, or even uncover a previously silent disease.