AB - The anti-asthmatic effect of theophylline may supplement those of inhaled steroids in asthma. The aim of the present trial was to study how the addition of theophylline compares to doubling the dose of inhaled steroid in asthmatics who remain symptomatic on beclomethasone dipropionate (BDP) 400 μg/day. The trial was designed as a randomized, double-blind, parallel-group study in several European countries. 69 patients were treated for 6 weeks with theophylline plus BDP 400 μg/day, compared to 64 patients treated with BDP 800 μg/day. The mean ± SD serum theophylline concentration was ± mg/l. Lung function measurements were made throughout the study and patients kept daily records of peak expiratory flow rate (PEF), symptoms and salbutamol usage. Forced expiratory volume in one second and PEF at week 6 were significantly increased by both treatments (p <). PEF variability was reduced by about 30% in both groups. There were significant improvements in asthma symptoms and rescue medication use (p <). There were no significant differences between the treatment groups. The study demonstrated clinical equivalence of theophylline plus beclomethasone dipropionate 400 μg/day and beclomethasone dipropionate 800 μg/day in patients whose asthma is not controlled on beclomethasone dipropionate 400 μg/d. The results support the use of theophylline as steroid-sparing agent. The combination of low-dose inhaled steroid plus theophylline is a suitable treatment for moderate asthma.