OBJECTIVES: To determine if primary care physician’s (PCP) prescribing behavior varies across brand name and generic drugs depending on each patient’s eligibility for the Federal 340B program. METHODS: Prescription claims from 10 in-clinic pharmacies in Orange and Los Angeles counties were used to identify 63,384 non-HIV patients who filled 640,480 new prescriptions between 2013 and 2015. Patients were identified as ineligible for the clinic’s 340B program if their claims were processed by fee-for-service state Medicaid (FFS Medicaid). We use Logistic models to analyze the likelihood that a brand name drug was utilized controlling for 340B eligibility, patient characteristics and drug therapeutic class. RESULTS: PCPs were less likely to prescribe brand name drugs to 340B-eligible patients (OR=0.537, 95% CI = 0.523-0.551) than FFS Medicaid patients who were ineligible for 340B pricing. The likelihood of brand name prescribing increased monotonically over age 35: 35~49 years (OR=1.253, 95% CI=1.227-1.281), 50~64 years (OR=1.351, 95% CI=1.324-1.378), 65+ years (OR=1.709, 95% CI=1.671-1.748). Males were more likely to receive brand name drugs (OR=1.185, 95% CI=1.169-1.200) than females. Patients lived in Orange County were more likely to receive brand name drugs than Los Angeles County (OR=1.093, 95% CI=1.071-1.114). Meanwhile, 340B eligible patients and other clinic patients exhibited a lower likelihood of receiving brand name drugs relative to FFS Medicaid patients in all drug classes. CONCLUSIONS: