Is there a correlation between the contractual mechanisms used by managed care delivery systems and physicians' practice styles and referral patterns? Researchers at Boston University hypothesized that managed care financial incentives influence physician practice behavior beyond what could be expected from physician selection of managed care environments. Using data from the CTS Physician and Household Surveys, AMA Socioeconomic Monitoring System (SMS) physician survey data, and the managed care industry, the study examined whether physician practice patterns, such as referral patterns, scope of practice, and case mix differ in a managed care environment, or whether managed care simply attracts physicians with more conservative practice styles. The goal of the study was to inform the field on how managed care influences physician practice styles.