PURPOSE: The aim of this study was to assess whether the quality of diabetes care differs among practices employing nurse-practitioners (NPs), physician's assistants (PAs), or neither, and which practice attributes contribute to any differences in care. METHODS: This cross-sectional study of 46 family medicine practices from New Jersey and Pennsylvania measured adherence to American Diabetes Association diabetes guidelines via chart audits of 846 patients with diabetes. Practice characteristics were identified by staff surveys. Hierarchical models determined differences between practices with and without NPs or PAs. RESULTS: Compared with practices employing PAs, practices employing NPs were more likely to measure hemoglobin A(1c) levels (66% vs 33%), lipid levels (80% vs 58%), and urinary microalbumin levels (32% vs 6%); to have treated for high lipid levels (77% vs 56%); and to have patients attain lipid targets (54% vs 37%) (P