These individuals also risk having their money and illicit goods stolen by others or being apprehended by the police. Two strategies can be employed by participants in illegal markets to balance risks and rewards. First, they can sell only to people they know or to people who know people they know. This substantially reduces the risk of being arrested or ripped off, but it restricts sales and buying opportunities. Second, they can sell to strangers; this approach provides access to more customers for the seller and allows shopping by the buyer, but it increases participant risk of arrest and rip off. The two approaches to marketing illicit goods and services result in very different geographic patterns of retail marketplaces, types of places used, and relationships between illicit retailing and licit routine activities. A general model of the geography of illicit retail marketplaces is used to explain the two approaches and why they produce different results. Data from a study of drug markets in San Diego, California, show the plausibility of the general model. Implications of the general model for prevention, control, displacement, and research on illicit retail markets are discussed. An appendix contains supplemental information on the impact of illicit activities on property values. 15 references, 3 notes, and 3 tables