Illicit drugs other than marijuana have a unique and important place in the picture of adolescent substance use and associated problems. Large, epidemiological studies have revealed that, although the use of individual drugs (other than marijuana) may fluctuate widely, the proportion of adolescents using any of them has been more stable in the decade between 2000 and 2010, compared to decades prior. In this chapter, we give an overview of illicit substance use in adolescence, including cocaine/crack, methamphetamine, heroin, ecstasy, MDMA, LSD, and GHB. We review epidemiological patterns of use among youth, including modes of use and common trajectories of use. We discuss cognitive, behavioral, and social contexts of other drug use in adolescence, and we review demographic patterns of use. We conclude by reviewing similarities and differences between substances.