Six patients with a clinical picture of inhaled foreign body and normal chest radiograph were selected for a study with Xenon 133 screening of the lung. The scan was positive in 3 cases from whom a foreign body was removed. The remaining 3 cases in whom the scan was negative were discharged and an uneventful follow-up was recorded. Xenon 133 scanning was found to be useful in the selection of patients for bronchoscopy.