Recently there has been increased interest in the role of bronchodilators in the maintenance therapy of asthma in childhood. We report the use of slow-release aminophylline (Phyllocontin Continus tablets) in childhood asthma. Ten patients, all of whom were receiving disodium cromoglycate (DSG), were given a single dose of Phyllocontin tablets (12.5 mg/kg) and observed over a period of 8 hours. Measurements of peak flow rate (PFR) and forced expiratory volume in one second (FEV1) showed an increase of at least 30% at 3 to 5 hours and the improvement continued to 8 hours. No effect was noted on heart rate. Ten patients were assessed over a 4-week period on DSG then over two 4-week periods on Phyllocontin tablets and placebo on a double-blind crossover basis. The dosage of Phyllocontin tablets used was 12.5 mg/kg twice daily. Using twice daily PFR recordings there was no significant difference between the two periods on DSG and Phyllocontin tablets. The reduction in PFR during the period on placebo was significant, however, and more markedly so between the period of placebo and the period on Phyllocontin tablets. We conclude that Phyllocontin tablets in these patients compared favourably with DSG in the maintenance therapy of asthma in childhood. The results obtained after single dose administration also suggest that a proportion of children with asthma may benefit from combined treatment with DSG and regular bronchodilators.