After an analysis of the six drug markets, this study advises that the overarching aim of preventive action against drug markets is to ensure the number of buyers using the market falls short of the threshold population needed to sustain that market. Providing treatment services is a demand reduction strategy that involves reducing the value of illicit drugs to buyers, rather than increasing their costs. Research shows that a range of treatment options can be cost-effective. Although the medical and ethical considerations in substitute prescriptions are complex, it is clear that community safety benefits can be achieved through a more flexible and responsive prescription regime through the National Health Service. The more that users' prescriptions approximate their ideal, the less they will be drawn to illicit drugs that are funded by acquisitive crime or drug dealing. Drug markets can also be disrupted by low-level law enforcement. Forty-four percent of the drug users interviewed in this study said that the risk of enforcement was a crucial factor when deciding which drug market to use and when to use it. The third strategy, situational prevention, involves measures directed at specific behaviors related to the management, design, or manipulation of the immediate environment in which the behaviors occur. Four main types of situational measures can be applied to drug markets: measures that are adjuncts to enforcement, those that reduce the amenities of the markets to buyers and sellers, measures that interrupt the street drug scene, and measures to reduce the threshold population by addressing street prostitution. 9 figures, 1 table, 24 references, and appended discussion of the private prescription system