Hospitalists are the fastest-growing medical specialty in the US, but their effect on quality of inpatient care has not been comprehensively assessed. This large observational study compared outcomes of patients cared for by hospitalists, general internists, and primary care physicians. Inpatient mortality and readmission rates were similar across all three groups of patients, and while hospitalists' patients had a slightly shorter length of stay, costs of care were also similar across groups. The study also did not find a relationship between case volume and outcomes.