ABSTRACT.Objective. To evaluate and analyze the existing evidence for the diagnosis and treatment of acute uncomplicated sinusitis in children.Design. A systematic overview and meta-analysis considered all pertinent studies with at least 10 children younger than 18 years with acute symptoms of <30 days and without serious complications.Outcomes. Clinical improvement rates for intervention studies of antibiotics or ancillary measures; concordance of diagnostic tests (expressed as likelihood ratios).Results. Of 1857 citations originally reviewed, we identified 21 qualifying studies, compared with 450 reports on complications of acute sinusitis and 233 nonsystematic reviews of the subject. The qualifying studies included 5 randomized, controlled trials and 8 case series on antibiotic therapy, 3 randomized, controlled trials on ancillary treatments, and 8 studies with information on diagnostic tests (including 3 therapeutic trials). Definitions and inclusion criteria were heterogeneous across studies. The pooled clinical improvement rate with antibiotics was 88% (177/202) in randomized, controlled trials and 92% (318/345) in nonrandomized studies; the improvement rates on no antibiotics were 60% and 80%, respectively. Improvement rates were significantly higher in nonrandomized studies (Mantel-Haenszel odds ratio: 1.79; 95% CI: 1.05-3.04, stratified for use of antibiotics). Data on ancillary measures were sparse and heterogeneous. In studies comparing clinical findings with plain film radiography, the pooled rate of abnormal radiographic findings against a clinical diagnosis of sinusitis was 73% (596/814; range: 55% to 96% between studies). There was poor concordance between clinical criteria, plain radiographs, ultrasonography, computed tomography, and fluid on aspiration in all available paired assessments (all positive likelihood ratios were <4 and all negative likelihood ratios were >0.2).Conclusions. Good, high-quality evidence for acute uncomplicated sinusitis in children is limited. Diagnostic modalities show poor concordance, and treatment options are based on inadequate data. More evidence is needed for defining the optimal treatment and diagnostic methods for this common condition.