The research team will administer a brief survey to ascertain behavioral, psychosocial, and clinical factors that may be related to non-prescription fentanyl (NPF) exposure among young people who use illicit drugs. The researchers will also characterize knowledge of and perceptions towards drugs contaminated with NPF, as well as the potential diversion of prescription fentanyl formulations (e.g., transdermal patches). After the interviewer-administered survey has been completed, participants will provide urine samples to determine recent exposure to NPF and other illicit drugs.