One hundred and twenty-eight erect radiographs of the thorax in 42 children with bronchial asthma have been analysed. The criterium for inclusion in this study was the demonstration on once occasion at least of hyperinflation of the lung with a low diaphragm, increased size of lung, narrow heart and increase in the retrosternal transparent area. In all patients there was narrowing of the vessels. In addition, the vessels appeared irregular and curved. Other characteristic radiological findings were tram-lines, obstructed bronchi, peribronchial infiltrates and atelectases. Increasing severity of the attack lead to increasing finding of other radiological changes in the thorax, but these have not yet been statistically examined.