Drug prohibitionists support their argument against drugs by claiming that drugs are potent, mind-altering, and dangerous and that drug use leads to undesirable and illegal behavior. They also believe that less potent drugs such as marijuana are gateway drugs that will lead the user to become an abuser of drugs such as heroin. In contrast, an economic analysis of potency predicts that prohibition increases the potency of dangerous drugs and makes them more deadly to consume. Substantial historical data support this prediction. The underground market for illegal drugs has been transformed from relatively benign drugs to hazardous drugs such as cocaine and heroin. Increased drug law enforcement efforts and penalties have been accompanied by increases in the potency of illegal drugs. However, the data also suggest some positive prospects for the renewed legalization of drugs. Legalizing drugs does not simply reduce the price and increase consumption and addition; instead, it completely transforms these drugs and their markets and results in drug products of lower potency, higher quality, and greater safety for the consumer. The economic model of potency predicts that the relegalization of drugs would reverse the trends in drug potency, perhaps resulting in significant improvement in the health and safety of consumers. Figures, notes, and 41 references (Author abstract modified)