Much empirical evidence indicates that the popularity of various drugs tends to increase and wane over time producing episodic epidemics of particular drugs. These epidemics mostly affect persons reaching their late teens at the time of the epidemic resulting in distinct drug generations. This article examines the drug generations present in the 2000s among arrestees in the 10 locations served by the Arrestee Drug Abuse Monitoring–II program. At all 10 locations, the findings show that crack use is still common among older arrestees but not among arrestees born more recently. Marijuana is the drug most common among younger arrestees. The article also examines trends in heroin, methamphetamine, and powder cocaine use among arrestees at the few locations where their use was substantial. Abstract published by arrangement with Sage Journals.