Acute sinusitis is a common illness in primary care. Studies have demonstrated the difficulty of making the differential diagnosis of acute purulent sinusitis based on clinical evaluations alone. This leads to a significant overuse of antibiotics, which in turn may contribute to increased bacterial resistance. In most cases, GPs have to base their differential diagnosis of sinusitis on clinical signs and symptoms and examination of the patient. The aim of this review is to assess which clinical signs and symptoms can predict an acute purulent sinusitis, compared with accepted reference standards. A review of the literature was performed by looking at articles related to the diagnoses of acute sinusitis in general practice. The following search criteria were used: unselected general practice population; objective reference standard; and logistic regression to evaluate symptoms and signs independently associated with the diagnosis. Four studies were identified for further analysis. The following symptoms and signs were associated with acute purulent sinusitis: purulent secretion as a symptom experienced by the patient or as a sign demonstrated in the nasal cavity by the doctor; pain in the teeth; pain at bending forward, and two phases in the illness history. An elevated erythrocyte sedimentation rate and increased C-reactive protein also contributed to the diagnosis. By use of the specified signs and symptoms the GP can increase the probability of correctly diagnosing an acute purulent sinusitis and reserve antibiotic prescription for these patients.