Objective: The U.S. Centers for Medicare and Medicaid Services (CMS) generally pays for non-institutional-based services and supplies “incident to” a physician's professional service. This study explores the concept of incident-to, the regulations and guidance surrounding its use and presents practical considerations for physicians. Methods: Incident-to guidance provided by CMS was collected, arranged in order of issuance, abstracted and analyzed. A compilation of relevant resources, a glossary and checklist tool were also created as part of the project. Results: Federal regulations at 42 CFR 410.26(b) specify criteria for “incident to” services. Medicare Part B pays for services and supplies incident to the service of a physician, including drugs or biologicals that are not usually self-administered. The services and supplies must be furnished in a non-institutional setting to non-institutional patients and be of an integral, though incidental, part of the service of a physician in the course of diagnosis or treatment of an injury or illness. They are also provided without charge or included in the bill of a physician. Such services are typically performed by non-physician staff however require direct personal supervision by the physician. The U.S Office of the Inspector General (OIG) has announced incident-to services as an area of study in their 2008 Work Plan. Conclusion: The concept of incident-to services is commonly misunderstood and may therefore present a Medicare compliance risk for physicians. It is essential for physicians and their practice decision-makers to understand and apply the CMS regulations surrounding incident-to services in order to appropriately bill and be reimbursed by Medicare for the provision of Part B separately payable drugs in non-institutional settings.