Dynamic spirometry and peak expiratory flow were measured in 297 school-aged children with asthma during their control visit at the outpatient clinic in 1993. Sixty (20%) children had no maintenance drugs, 169 (57%) used cromoglycate (n = 97) or nedocromil (n = 72), and 68 (23%) budesonide. The treatment of each child had been selected on clinical grounds according to the principles of the international consensus statement from 1989. The mean values of peak expiratory flow (PEF), forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were over 95% of the height-related reference values in all treatment groups. The lower limits of the 95% confidence intervals were at the level of more than 90% of those predicted. The mean FEV1/FVC ratio (FEV%) was over 85%, and the mean maximal mid-expiratory flow (MMEF) over 75% of the reference values. Decreased PEF values ( < 75%) were present in 10%, decreased FVC, FEV1, or FEV% ( < 75%) values in 4.6%, and decreased MMEF ( < 65%) values in 18%. Only minor differences between the different therapeutic groups were observed. Our results show that the clinical selection of children between the three therapeutical groups was adequate. In our area up to 70% of children requiring maintenance therapy for asthma can be treated with cromones.