HMO: the concept, new evidence, implications

HMOs have been the most controversial alternative healthcare delivery system in the US. As a first step towards understanding the concept and state of HMOs, a description is offered, including a review of basic characteristics, types, and general financial incentives and disincentives. Although the performance of HMOs has also been the subject of recent debate, there is evidence that studies of performance have been inconclusive, and while observations about the effects of HMOs appear frequently in the literature, the causes are not actually known. To provide more conclusive information on the performance of HMOs, the American Medical Association conducted several related studies during the tenure of the authors. Results and implications of these studies are presented.