Background: Pneumonia is the leading cause of mortality in children under five years of age. Treatment of pneumonia requires an effective antibiotic used in adequate doses for an appropriate duration. Recommended duration of treatment ranges between 7 and 14 days, but this is not based on any empirical evidence. Shorter duration of therapy, if found to be effective, could be particularly important in resource-poor settings where there is a high risk of death, poor access to medicines and health care, and limited budgets for medicines. Objectives: To evaluate the efficacy of short-course versus long-course therapy with the same antibiotic for non-severe community-acquired pneumonia in children aged 2 to 59 months. Search strategy: We searched The Cochrane Central Register of Controlled Trials (CENTRAL); the Database of Abstracts of Reviews of Effects (DARE) (The Cochrane Library, 2007, Issue 3); MEDLINE (OVID) (January 1966 to September 2007); EMBASE (Embase.com) (1974 to September 2007); and LILACS (1982 to September 2007). Selection criteria: All randomized controlled trials (RCTs) evaluating the efficacy of short-course versus long-course therapy using the same antibiotic for non-severe community-acquired pneumonia in children. Data collection and analysis: Two review authors independently assessed trial quality and extracted the data. Main results: Three studies (5763 children) were included. Analysis of three days versus five days of treatment with the same antibiotic for non-severe pneumonia in children showed non-significant differences in rates of clinical cure at the end of treatment (RR 0.99; 95% CI 0.97 to 1.01), treatment failure at the end of treatment (RR 1.07; 95% CI 0.92 to 1.25) and relapse rate after seven days of clinical cure (RR 1.09; 95% CI 0.83 to 1.42). Subgroup analysis evaluating the impact of different antibiotics showed non-significant differences for these outcomes with different durations of therapy. Authors' conclusions: The evidence of this review suggests that a short course (three days) of antibiotic therapy is as effective as a longer treatment (five days) for non-severe pneumonia in children under five years of age. However, there is a need for more well-designed RCTs to support our review findings.