The challenges presented by managed care arrangements and third-party utilization controls have led hospitals to strengthen internal utilization management programs. This article reports findings from a set of case studies on how hospitals have adapted their utilization management programs to their environments. While knowledge acquired from case studies should not be overgeneralized, the findings of these studies suggest some lessons that merit consideration by hospitals advancing their own programs in utilization management.Utilization management is usually defined as a program to ensure that hospital admissions are clinically appropriate, that medical services are provided in accordance with norms of practice, and that guidelines for reimbursement are followed. The literature contains a growing number of case studies of effective utilization review programs. For example, Mozes et al.(1) found that the application of standardized criteria through daily review at one hospital reduced average length of stay by nearly two days. Catchpole (2) found that the introduction of a utilization management program reduced lengths of stay for 70% of matched cases. And Woodside et al. (3) found that an intensive review program reduced lengths of stay by almost three days.Despite these case studies and the great number of articles, books, and guidelines that have been written on how the mechanics of the utilization reuiew process operates, precious little attention has been paid to how the entire utilization management program should relate to broader hospital strategies, including physician-hospital relations. Do some general principles exist in designing effective utilization management programs, or does each hospital require a unique approach?As a step toward understanding how various elements of hospital utilization management programs contribute to effective results, case studies of Michigan hospitals were conducted in cooperation with the Sisters of Mercy, Farmington Hills. The purpose of these studies was to identify relevant factors, in addition to the mechanics of utilization review, that contributed to effective operations. Preparing the case studies involved reviewing internal and external reports on utilization experience, interviewing hospital personnel associated with utilization management programs and general administration, and interviewing representatives of third parties involved in hospital reimbursement and utilization review.Following a brief description of environmental conditions in Michigan common to all study hospitals, findings in five areas of hospital utilization management programs are presented along with ten lessons for effective utilization management. While knowledge acquired from case studies should not be overgeneralized, we believe that these lessons merit consideration by hospitals interested in advancing their own utilization management programs.