 Through its clinical research protocols, the NIDA IRP attempts to: elucidate the nature of drug abuse and addiction; determine the potential use of new therapies, both pharmacological and psychosocial; and decipher the long-term effects of drugs of abuse on the development, maturation, function, and structure of the brain and other organ systems. In support of the IRPs work, the scientific goal of this screening protocol is to assess potential research participants eligibility for NIDA IRP research studies. Screening will include medical and psychological tests and procedures. The data collected during screening are a unique and valuable source of information that aids in NIDAs mission. Therefore, a secondary goal of this protocol is to obtain data that characterizes the population of subjects contacting NIDA about research participation and to analyze data so obtained, such as that on the prevalence and consequences of HIVAIDS, viral hepatitis, and related diseases. 