Human Immunodeficiency Virus (HIV) infected patients in the Kaiser Permanente HIV registry wil be followed in the usual clinical care to estimate the rates of specified clinical events. The rates will be stratified by relevant characteristics like age, CD4 counts, HIV Viral Load (VL), HIV medication history. The rates in the HIV infected cohort wil be compared with the rates of these events in patients in the Kaiser Permanente database who are not infected with HIV.