To what extent do hospitals reduce provision of uncompensated care in response to fiscal pressure emerging from growth in managed care market share? This study produced simulations that predict how much uncompensated care hospitals provide under different managed care growth scenarios. The researchers constructed a core analysis file from two large national data sets, the American Hospital Association annual survey and HCFA's 100 percent MEDPAR file. They supplemented these data with additional managed care penetration data and CPS (Census) data. They estimated the effects of managed care penetration on hospital uncompensated care at the national and state levels. The objective of this study was to inform policy makers about what consequences their decisions related to promoting or discouraging managed care may have on hospitals' provisions of uncompensated care.