Objective. - To review and discuss the differences and similarities between the use of crack cocaine and cocaine hydrochloride; and to determine how these findings might affect policies on the imprisonment and treatment of cocaine users. Data Sources. - English-language publications were identified through a computerized search (using MEDLINE) between 1976 and 1996 using the search terms 'smoked cocaine,' 'crack cocaine,' 'freebase,' and 'cocaine- base.' In addition, manual searches were conducted on references cited in original research articles, reviews, and an annotated bibliography, and on selected journals. Study Selection. - Only those articles that compared various routes of cocaine administration or types of cocaine (cocaine base or crack cocaine vs cocaine hydrochloride) were examined. Data Extraction. - Studies were reviewed to obtain information on the composition of the 2 forms of cocaine, and the prevalence, pharmacokinetics and pharmacodynamics, abuse liability, pattern of use, and consequences across the various routes of cocaine administration and forms of cocaine. Conclusion. - Cocaine hydrochloride is readily converted to base prior to use. The physiological and psychoactive effects of cocaine are similar regardless of whether it is in the form of cocaine hydrochloride or crack cocaine (cocaine base). However, evidence exists showing a greater abuse liability, greater propensity for dependence, and more severe consequences when cocaine is smoked (cocaine-base) or injected intravenously (cocaine hydrochloride) compared with intranasal use (cocaine hydrochloride). The crucial variables appear to be the immediacy, duration, and magnitude of cocaine's effect, as well as the frequency and amount of cocaine used rather than the form of the cocaine. Furthermore, cocaine hydrochloride used intranasally may be a gateway drug or behavior to using crack cocaine. Based on these findings, the federal sentencing guidelines allowing possession of 100 times more cocaine hydrochloride than crack cocaine to trigger mandatory minimum penalties is deemed excessive. Although crack cocaine has been linked with crime to a greater extent than cocaine hydrochloride, many of these crimes are associated with the addiction to cocaine. Therefore, those addicted individuals who are incarcerated for the sale or possession of cocaine are better served by treatment than prison.