OBJECTIVE: To assess whether advance directives influence resource use by hospitalized patients. DATA SOURCES: A systematic search of computerized medical databases, reference lists from relevant articles, and personal files was conducted to identify studies examining the association between advance directives and resource use. STUDY SELECTION: Primary studies assessing the effect of advance directives on hospital resource use were selected if they had a clear quantitative measure of hospital resource use, hospitalized patients as a study population, a control group for comparison, and a description of the advance directive being studied. Data on the following topics were abstracted from studies meeting inclusion criteria: study methods and design, resource use, source of financial data, description of advance directive, population size and composition, length of assessment. SYNTHESIS: Six studies met inclusion criteria. Three retrospective studies showed significant reductions in resource use associated with documentation of advance directives while three prospective studies (two randomized, one not randomized) showed no association between advance directives and reduced resource use. Studies were limited to narrowly defined patient populations in US tertiary care hospitals. CONCLUSIONS: Little evidence supports the hypothesis that advance directives reduce resource use by hospitalized patients. Some retrospective studies have shown savings, but their conclusions are weakened by shortcomings in study design. Prospective trials, which have better experimental methods, have demonstrated no evidence of cost savings with the use of advance directives.