Inhaled corticosteroids are the most effective anti-inflammatory drugs for asthma. Leukotriene receptor antagonists are a new class of anti-inflammatory drugs that have the advantage of oral administration and the potential for better compliance compared with inhaled corticosteroids. This article summarizes evidence from randomized controlled trials, comparing the efficacy and tolerability of inhaled corticosteroids with those of leukotriene receptor antagonists in patients with persistent asthma. The evidence derived from a systematic review of randomized controlled trials confirms that patients treated with inhaled corticosteroids of chlorofluorocarbon-propelled beclomethasone 400 mug/day or fluticasone propionate 200 mug/day have better asthma control than those treated with oral leukotriene receptor antagonists. More specifically, treatment with inhaled corticosteroids is associated with 65% fewer exacerbations requiring systemic corticosteroids, greater improvement in spirometry and symptoms, fewer night-time awakenings and less use of rescue beta(2)-adrenoceptor agonists. This review does not identify any difference in short-term safety between inhaled corticosteroids and leukotriene receptor antagonists. Although adverse effects typically associated with inhaled corticosteroids (such as growth suppression, osteopenia, and adrenal suppression) were not measured, preventing a fair comparison of the safety profile on long-term use.In conclusion, the scientific evidence does not support the substitution of leukotriene receptor antagonists for low doses of inhaled corticosteroids, which should remain first-line therapy for asthma control.