Using qualitative and quantitative methods, the authors develop and test hypotheses about the impact of hospitalists on efficiency and quality of care relative to teaching teams. Departure of actual from self-perceived benefits for hospitalists, both individually and collectively, is studied. It was found that hospitalists are, on average, more efficient diagnosticians and/or enhance throughput, as evidenced by having relatively lower charges, through reductions in testing and length-of-stay, than teaching teams. Much of that benefit is concentrated among patients admitted by intensivists. The authors find little evidence of quality focus or of greater use of community resources among hospitalists. Indeed, hospitalists were found to have no effect on the choice of postdischarge outlets. The authors document variation in care delivery among hospitalists. In particular, it was found that among hospitalists there is more variation in achieving shorter length of stay but less variation in use of diagnostic testing.