This introduction presents an overivew of the key concepts discussed in the subsequent chapters of this book. The book provides an overview into the complex issues in HIV and mental health and illness. The fields of public health and mental health have theoretically been collaborating since the beginnings of Community Psychology. The prevalence of mental illness has also been found to be high among seropositive individuals. Co-morbid substance abuse is common among HIV positive individuals with severe mental illness, resulting in serious adverse effects. The availability of more effective HIV treatments has reduced mortality, resulting in a growing number of people living with HIV, even as the incidence of new cases decreases in the United States. With the inception of new pharmacotherapies and the advent of highly active retroviral therapy (HAART) drug regimens, a growing number of persons with HIV or AIDS have experienced greatly increased longevity and have joined the ranks of those living with a chronic illness.