We did a meta-analysis of randomised controlled trials (RCTs) to assess the therapeutic role of antibiotics for acute sinusitis compared with placebo. Eligible studies were retrieved from PubMed and Scopus. 17 double-blind RCTs were included (three involving children). Acute sinusitis was diagnosed with clinical criteria in nine RCTs, imaging studies in six RCTs, and microbiological or laboratory methods in two RCTs. Amoxicillin was used in ten of 23 antibiotic treatment groups. To account for potential statistical heterogeneity between studies, a random-effects model was used for all analyses. Compared with placebo, antibiotics were associated with a higher rate of cure or improvement (2648 patients, odds ratio [OR] 1.64 [95% CI 1.35-2.00], data from 16 RCTs), or cure alone (1813 patients, OR 1.82 [1.34-2.46], 12 RCTs), but also with more adverse events (1963 patients, OR 1.87 [1.21-2.90], 12 RCTs). The rate of symptom resolution was faster with antibiotics in most RCTs. Disease complications, disease recurrence, and study withdrawals because of adverse events did not differ between compared treatments. In conclusion, use of antibiotics for acute sinusitis confers a small therapeutic benefit over placebo with a corresponding rise in the risk for adverse events. We suggest that antibiotics should be reserved for carefully selected patients with a higher probability for bacterial disease.