Evaporation of Tc-99m pertechnetate at about 2500 degrees C on a carbon surface generates an ultrafine aerosol of Tc-99m-labeled carbon clusters (Technegas). The small particle size of about 100 nm enables the aerosol to behave similarly to a gas in its ability to penetrate. After inhalation, the radioactive particles adhere to the walls of the respiratory bronchioles and alveoli, or to the greater bronchial tubes if the airflow is not laminar. The high concentration of radioactivity in the argon carrier gas makes it possible to perform inhalation scintigraphy after only a few breaths. The authors investigated 24 infants with multiple events of bronchitis, most of whom had pneumonia. Seventeen patients had inhalation scintigraphy and bronchoscopy. Of these, 11 had scans diagnostic of bronchial stenosis and 6 had normal scans. Except for two pathologic scans, all scintigraphic findings matched well with the results of bronchoscopy. Seven patients had scintigraphy only, of which four were normal. Inhalation scintigraphy with Technegas is a reliable, nonhazardous procedure to preselect young patients for directed bronchoscopy.