OBJECTIVES: Debate continues on whether nurse practitioners (NPs) and physician assistants (PAs) are more likely to order ancillary services, or order more costly services among alternatives, than primary care physicians (PCPs). We compared prescription medication and diagnostic service orders associated with NP/PA versus PCP visits for management of neck or back (N/B) pain or acute respiratory infection (ARI). STUDY DESIGN: Retrospective, observational study of visits from January 2006 through March 2008 in the adult primary care practice of Kaiser Permanente in Atlanta, Georgia. METHODS: Data were obtained from electronic health records. NP/PA and PCP visits for N/B pain or ARI were propensity score matched on patient age, gender, and comorbidities. RESULTS: On propensity score-matched N/B pain visits (n = 6724), NP/PAs were less likely than PCPs to order a computed tomography (CT)/magnetic resonance image (MRI) scan (2.1% vs 3.3%, respectively) or narcotic analgesic (26.9% vs 28.5%) and more likely to order a nonnarcotic analgesic (13.5% vs 8.5%) or muscle relaxant (45.8% vs 42.5%) (all P ≤.05). On propensity score-matched ARI visits (n = 24,190), NP/PAs were more likely than PCPs to order any antibiotic medication (73.7% vs 65.8%), but less likely to order an x-ray (6.3% vs 8.6%), broad-spectrum antibiotic (41.5% vs 42.5%), or rapid strep test (6.3% vs 9.7%) (all P ≤.05). CONCLUSIONS: In the multidisciplinary primary care practice of this health maintenance organization, NP/PAs attending visits for N/B pain or ARI were less likely than PCPs to order advanced diagnostic radiology imaging services, to prescribe narcotic analgesics, and/or to prescribe broad-spectrum antibiotics.