In 1983 Congress adopted the most significant change in the Medicare program since its inception in 1965. Along with measures to ensure the solvency of the Social Security System into the next century, Congress approved a system of prospective payment for hospital inpatient services, whereby hospitals are paid a fixed sum per case according to a schedule of diagnosis related groups (DRGs). The program will be phased in over a four-year period that began October 1, 1983. Several types of hospitals and distinct part units of general hospitals are excluded from the system until 1985, when Congress will receive a report on a method of paying them prospectively. Information used to calculate the DRG rates was published September 1, 1983, as part of the interim final regulations. Other third party payers, such as state Medicaid systems and insurance companies, are considering converting to this method of payment, and several have adopted it. The implications for occupational therapy include a greater emphasis on reducing hospital length of stay, expanding outpatient care, increasing productivity, and a trend toward documentation and accounting consistent with computer technology.