Twenty patients were studied to assess the value of aerosol ventilation scintigraphy, using 99Tcm diethylene triamine penta-acetic acid (DTPA) as a screening test for bronchiectasis. All patients had previously undergone bronchography for suspected bronchiectasis. Nine had cylindrical bronchiectasis and 11 had no demonstrable abnormality. Only two of the 20 patients had features suggestive of bronchiectasis on their chest radiographs. Segmental defects in ventilation were demonstrated by scintigraphy in five of the nine patients with bronchiectasis (56%). Regional ventilation appeared normal in 26 of the 27 lungs which were bronchographically normal (96%). Whilst the sensitivity of aerosol ventilation scintigraphy in detecting bronchiectasis is low (56%), it compares favourably with that of the chest radiograph (22%) in this group of patients with mild disease and non-specific symptoms. Thus, in some, it may obviate the need for bronchography.