The physician's important decision-making role in the allocation of medical resources is well recognized. An important part of this role is one physician's decision to refer a patient to another physician for care. Existing research, largely descriptive in nature, has been limited by lack of a clear theoretical and conceptual framework for analysis. The current paper develops and tests a model of physician referral behavior based on exchange theory. Differences in rates of referral among physicians are viewed as a function of the different rewards and costs perceived by physicians occupying different levels of status within a given medical community. The model is tested using data collected from 127 internists in private practice in the northern suburbs of Chicago. Findings are discussed in terms of policy issues and suggestions for further research are indicated.