OBJECTIVE To assess the likelihood of antimicrobial streamlining between 2 antimicrobial stewardship methods. DESIGN Retrospective cohort study. SETTING Large academic medical center. METHODS Frequency and time to antimicrobial streamlining were compared during a prior authorization and a prospective audit period. Streamlining was defined as an antimicrobial change to a narrower agent if available or to a broader agent if the isolate was resistant to empiric therapy. Patients included were ≥18 years old with monomicrobial bacteremia with S. aureus, Enterococcus spp., or any aerobic Gram-negative organism. RESULTS A total of 665 cases of bacteremia met inclusion criteria. Frequency of streamlining was similar between periods for all cases of bacteremia (audit vs restriction: 60.7% vs 53.2%; P=.12), S. aureus bacteremia (73.2% vs 76.9%; P=.671), and Enterococcus bacteremia (81.6% vs 71.9%; P=.335). Compared to restriction, the audit period was associated with an increased frequency of streamlining for cases of Gram-negative bacteremia (51.4% vs 35.6%; odds ratio [OR], 1.85; 95% confidence interval [CI], 1.06-3.25), those on the medical service (67.9% vs 53.1%; OR, 1.86; 95% CI, 1.09-3.16), and those admitted through the emergency department (71.6% vs 51.4%; OR, 2.32; 95% CI, 1.24-4.34). Characteristics associated with increased streamlining included: absence of β-lactam allergy (P<.001), Gram-negative bacteremia (P<.001), admission through the emergency department (P=.001), and admission to a medical service (P=.011). CONCLUSIONS Compared with prior authorization, prospective audit increased antimicrobial streamlining for cases of Gram-negative bacteremia, those admitted through the emergency department, and those admitted to a medical but not surgical service. Infect Control Hosp Epidemiol 2016:1-7.