Hospital medicine has undergone remarkable growth since its creation. Most (but not all) of the published literature demonstrates better outcomes for patients cared for by hospitalists. We performed a systematic review and meta-analysis to estimate the magnitude of the impact of hospitalists on length of stay (LOS) and cost. Medline/PubMed. Articles published through February 2011 comparing outcomes (LOS and/or cost) of hospitalists with others. Two reviewers independently searched for abstracted information. We also contacted individual authors to provide us with missing data. We used a random-effects model. A total of 502 abstracts were initially identified and 17 studies of 137,561 patients were included in the final analysis. LOS was significantly shorter in the hospitalist group compared with the non-hospitalist group, with a mean difference of -0.44 days (95% confidence interval [CI] -0.68 to -0.20, P < .001). In studies that compared a (non-resident) hospitalist service with a (non-resident) non-hospitalist service, LOS was also significantly shorter in the hospitalist group (mean difference -0.69 days [95% CI -0.93 to -0.46, P < .001]). Cost was not found to be significantly different (11 studies). There was significant heterogeneity between studies and we found no evidence of publication bias. Despite its limitations, our analysis supports the conclusion that hospitalists significantly reduce LOS without increasing costs. These findings can be used to define and measure expectations of performance for hospital medicine groups.