The most frequently diverted substances are hydromorphone, cocaine, meperidine, methadone, morphine, oxycodone, various amphetamines, and numerous other controlled drugs. The basic means of this diversion is the prescribing by physicians and osteopaths for individuals at such quantities and at such frequencies as to constitute a nontherapeutic use. Unscrupulous pharmacists divert those controlled substances which can be prescribed by telephone. Hospital nurses sign substances out correctly to patients, then divert them for their own use. Local law enforcement officers should watch for clues such as an influx of individuals into the area from a different socioeconomic strata and an increasing amount of pharmaceutical controlled substances appearing in various arrests or in undercover purchases made from street dealers. Other clues may be increasing numbers of complaints of prescription forgery and pharmacy or practitioner office reports of substance theft. They should also observe increasing use of certain practitioners by a segment of the population and increased purchase of controlled substances by practitioners. Enlisting the aid of trusted local pharmacies is recommended if physicians are suspected. Use of informants, undercover purchasers, and audits are other law enforcement strategies. The assistance of the Drug Enforcement Administration is also recommended.