The recurring decision of selecting among potential knowledge resources was modeled as a cost-benefit tradeoff, with associated observable features. Internal medicine and community family practice physicians (n = 228) completed a self-administered questionnaire designed to elicit reported use and cost-benefit features of nine knowledge resources. The subjects reported most frequent use of clinical colleagues, intermediate use of textbooks and journals, and least use of indexing systems. Resources' benefit-related qualities (extensiveness and credibility) were not related to reported use. In contrast, the model's access cost variables (availability, searchability, understandability, and clinical applicability) were significantly related to use. Results were generally favorable to the model's framework of knowledge resource selection. Multiple linear regression analysis suggested that physicians' use of clinical knowledge resources could be described by the physician's level of training, availability, applicability, and the resource medium (colleague, index, or text/journal).