While the states engaged in an extended period of adopting and revising laws regulating managed care during the 1990s, there has been to date only limited empirical assessment of the impacts of these laws. For this analysis, we constructed a data set using information on state laws combined with survey responses of physicians. We distinguish regulations with a typology based on whether they affect the context or content of care and the target group of the regulation (consumer or provider). Our findings indicate that the context of care appears to be more efficaciously regulated than the content of care. Provisions concerning consumer access and contractual relationships lead to greater reported physician ability to obtain referrals and services, improved quality of clinical interactions, and greater perceived clinical autonomy. Regulations intended to enhance professional autonomy are associated with lower reported levels of utilization constraints and higher reported quality of clinical interactions. In contrast, consumer protection provisions, including procedures for appeals from plan decisions, appear to have had little impact on most physicians' practices. Despite structural and legal constraints on the potential effectiveness of these regulations, state managed care legislation appears to have provided some protections against managed care restrictions on physicians' clinical autonomy.