Amounts billed for teaching physician services and paid by Medicare carriers were reviewed by the General Accounting Office (GAO) to determine whether such payments had been made only where the physicians had satisfied the requirements of the Social Security Act. Attention was focused on the requirement that teaching physicians must provide a personal and identifiable service to Medicare patients. To assess whether requirements were being met, GAO reviewed patients' medical records for randomly selected samples of Medicare patients from 10 hospitals and 9 states and additional information provided by hospitals. The review covered 8,917 services provided to 1,165 patients. GAO reviewed fee-for-service billings by teaching physicians for inpatient and outpatient services. Documentation for about half of the services, representing about 25% of the amount Medicare allowed, did not show whether the physicians had provided a personal and identifiable service. The inadequately documented services usually involved high-volume, low-cost services such as daily visits. The adequacy of Medicare documentation criteria and monitoring for compliance with Medicare requirements were addressed. Regulations being developed by the Health Care Financing Administration to implement new requirements are noted. Comments from the Social Security Administration and the Department of Health and Human Services are appended. (SW)