The Human Immunodeficiency Virus (HIV), which causes Acquired Immunodeficiency Syndrome (AIDS), is the leading infectious cause of adult deaths in the world. Given the scale of the epidemic, HIV/AIDS is now considered not only a health problem, but also a developmental and security threat. The incidence, survival and prevalence of disease are the most important variables to describe the impact of a disease. These variables are three different aspects of the same morbidity process and simultaneous consideration of all three is required to understand different aspects of the disease. Thus, This book is focused on distinct problems pertaining to estimation of HIV mortality rate, expected proportion of AIDS cases and survival function of clinically diagnosed AIDS patients under various conditions using parametric, nonparametric and semi-parametric techniques.The proposed statistical models are applied to data on HIV/AIDS patients from different countries. Our hope is that this work would help to better understand the trend of AIDS progression, to guide development of treatment strategies and and to take into account the roles of clinical factors in antiviral activities.