Concern about controlled substance diversion and overview of prescribers by legal and regulatory officials is growing. The article is designed to increase health professionals' awareness of the methods of diversion and to provide guidance on how diversion can be foiled. This paper also should help healthcare practitioners to better understand the regulations governing prescribing of controlled substances. Examples of unlawful prescribing of controlled substances are presented. Some behaviors of persons illegitimately seeking controlled substances from prescribers are described. Strategies to lessen the possibility of prescriptions being altered are discussed. Federal and state laws and regulations pertaining to controlled substances are described.