Drugs obtained and often manufactured illegally for the subjective effects they are said to produce. They are often distributed in urban areas, but are also available in suburban and rural areas, and tend to be grossly impure and may cause unexpected toxicity.

People who take drugs for a non-therapeutic or non-medical effect. The drugs may be legal or illegal, but their use often results in adverse medical, legal, or social consequences for the users.

Abuse, overuse, or misuse of a substance by its injection into a vein.

Usage of a single needle among two or more people for injecting drugs. Needle sharing is a high-risk behavior for contracting infectious disease.

Organized services for exchange of sterile needles and syringes used for injections as a potential means of reducing the transmission of infectious diseases.

Runaway and homeless children and adolescents living on the streets of cities and having no fixed place of residence.