. (1978). Thorax, 33,. Unilateral pulmonary collapse in asthmatics. Five asthmatic patients developed collapse of one lung. Three of the patients were children and three of the five had repeated episodes of atelectasis. Episodes of atelectasis were usually associated with localised chest pain, which was not pleuritic in character, and with breathlessness, but without wheezing. They were not related to clinically apparent respiratory infections or to deterioration of the underlying asthma. The cause is obscure, but re-expansion seems to be hastened by oral corticosteroid therapy.Atelectasis is a well-recognised complication of asthma. It is usually segmental or lobar and is said to be more frequent in children than in adults (Clarke, 1930;Hughes and Reisman, 1969;Crofton and Douglas, 1975 This girl had mild asthma from infancy until the age of 9 years but was then free of symptoms for three years. At the age of 12 she suddenly developed a fever, cough, and left-sided chest pain with no preceding wheeze or upper respiratory symptoms. Although she was breathless, no wheeze was heard, and the signs were those of collapse of the left lung. The radiograph showed collapse of the left lung with a prominent air bronchogram.There was no excess of eosinophils in the peripheral blood, and haemolytic streptococci were grown from mucopurulent sputum. The radiograph became normal after two weeks of treatment with penicillin and physiotherapy, and she remained symptom free for three months.She then developed wheeze and a cough, and a radiograph showed collapse of the lingula. Three days later there was also collapse of the left lower lobe. Prick tests against common allergens including Aspergillus fumigatus were negative, a sweat test was normal, and serum precipitins were not detected against A. fumigatus. At bronchoscopy the only abnormality seen was thick 'mucopus' in the left main bronchus. The aspirate contained no excess of eosinophils, and no fungi or bacteria were isolated on culture. The radiograph became normal after 10 days' treatment with physiotherapy and inhaled bronchodilators. She remained free of symptoms, but a chest radiograph one month later unexpectedly showed collapse of the left lower lobe, although she had no respiratory symptoms at that time. It was decided to treat this episode with corticotrophin (40 units twice weekly) and the radiograph returned to normal in three days.