The study first discusses the methodological issues of access to individual inmates, inmates' willingness to be interviewed, and the credibility of interview information. The validity of interview information involved a complex internal validity check and a comparison of interview information with information in the subject's presentence report. Interviews revealed few barriers to entry into the higher levels of cocaine and marijuana markets. Most of the subjects attained their positions of high-volume dealing without long apprenticeships or large quantities of capital. Revolving credit is the custom of the drug business. Profitable operations did not involve large or enduring organizations. Some segments of the markets had low levels of violence, and the wholesale market was national rather than regional. Findings suggest that drug markets consist of temporary and shifting coalitions of dealers rather than durable and hierarchical enterprises. Entry into drug markets is sufficiently easy such that new organizations can spring up to replace those incapacitated by effective enforcement. This tends to render ineffective those Federal enforcement strategies designed to cripple the drug market by incapacitating drug dealers presumed to operate large enterprises with a large share of the drug market. 3 tables and study instruments.