We undertook a community based case-control study to measure the effect of pranlukast on the reduction of inhaled steroid in adult asthmatics. Forty-one adults completed a run-in period of 4 weeks on 800 microgram of beclomethasone dipropionate (BDP) documenting twice daily peak expiratory flow (PEF) and symptom score and therapeutic score on a standard diary. Forced expiratory volume in one second (FEV1.0), V50, V25 was measured once during the run-in period. Patients were then randomized to receive either pranlukast with 400 microgram of BDP or 400 microgram alone for 8 weeks. There was no difference in the symptom score and therapeutic between the two groups at any time point. However, morning and evening % PEF run-in expressed as a % of the PEF average during the run-in period was significantly lower at 8 weeks in the groups without pranlukast. There were subjects in the group without pranlukast (35.3%) compared to those with (20.8%) who had a 10% or more reduction in % PEF from the run-in period. The patients with an FEV1.0 < 80% predicted who were randomized to the control group were more likely (5 of 7) to have a fall in % PEF run-in and those randomized to received pranlukast were less likely to have a fall in % PEF run-in though this was not significant (2 of 6). In this study, pranlukast has demonstrated steroid sparing effect. Severe asthmatics (FEV1.0 < 80%) who deteriorate after reduction of inhaled steroid may benefit most from pranlukast. Larger studies are now required to explore this important effect.