 This protocol describes the screening process used by the National Institute on Drug Abuse NIDA IRP to assess potential research participants eligibility for entering protocols of either the NIDAIRP. Through its clinical research protocols, the IRPs attempt 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 the IRPs 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 the IRPs missions. Therefore, a secondary goal of this protocol is to obtain data that characterizes the population of subjects contacting the IRPs about research participation and to analyze data so obtained, such as that on the prevalence and consequences of HIVAIDS, viral hepatitis, and related diseases. The population screened includes male and female adolescents ages 13-17 for NIDA only and adults age 18 for both IRPs. Screening procedures include standard medical and psychological tests and procedures are minimal risk. There is no direct benefit to subjects. Participants are paid for undergoing the screening process. 