In this article, we compared hospital efficiency using a multiple input-output approach in two ways: one way used a straightforward count of inpatient days and outpatient services as outputs; and the second used a case mix-adjusted count of inpatient services and outpatient care as outputs. Our results show that there was no difference when we incorporated the case-mix index, either as a weighting device or as a separate output. However, this result may be due to our having a relatively homogeneous sample, (i.e., large metropolitan hospitals). Variations using this approach may occur when using a more heterogeneous sample, such as comparing hospitals of all sizes or rural versus urban hospitals.