Purpose. To summarize the evidence comparing the effectiveness of short and long courses of oral antibiotics for infections treated in outpatient settings. Methods. We identified systematic reviews of randomized controlled trials for children and adults with bacterial infections treated in outpatient settings from Medline, Embase, CINAHL, Cochrane Database of Systematic Reviews and The Database of Review of Effects. Data were extracted on the primary outcome of clinical resolution and secondary outcomes. Results. We identified 30 potential reviews, and included 9. There was no difference in the clinical cure for children treated with short or long course antibiotics for Group A streptococcal tonsillopharyngitis (OR 1.03, 95% CI:0.97, 1.11); community acquired pneumonia (RR 0.99, 95% CI:0.97, 1.01); acute otitis media [<2 years old OR: 1.09 (95% CI:0.76, 1.57); ≥2 years old OR: 0.85 (95% CI:0.60, 1.21)]; or urinary tract infection (RR 1.06, 95% CI:0.64, 1.76). There was no difference in the clinical cure for adults treated with short or long course antibiotics for acute bacterial sinusitis (RR 0.95, 95% CI:0.81, 1.21); uncomplicated cystitis in non-pregnant women (RR 1.10, 95% CI:0.96, 1.25), or elderly women (RR: 0.98, 95% CI:0.62, 1.54); acute pyelonephritis (RR 1.03, 95% CI:0.80, 1.32); or community acquired pneumonia (RR: 0.96, 95% CI:0.74, 1.26). We found inadequate evidence about the effect on antibiotic resistance. Conclusions. This overview of systematic reviews has identified good quality evidence that short course antibiotics are as effective as longer courses for most common infections managed in ambulatory care. The impact on antibiotic resistance and associated treatment failure requires further study.