Methotrexate is a folic acid antagonist with proven anti-inflammatory properties. This originally led to its use in the therapy of some rheumatic and dermatological inflammatory disorders and, since the early 1980s, as a corticosteroid-sparing agent in the therapy of bronchial asthma. Although the exact anti-inflammatory mechanism is not known, it appears that in some patients with severe corticosteroid-dependent bronchial asthma, a reduction of at least 50% in the maintenance corticosteroid dosage can be achieved. Controversies regarding methotrexate efficacy may be a result of the small size and heterogeneity of the patient populations studied and the variable definition of corticosteroid "dependence'. Although the potential for serious short and long term adverse effects resulting from methotrexate therapy cannot be ignored, overall, methotrexate appears to be well tolerated at low dosages. Hepatic and pulmonary toxicity are the main adverse effects of concern. The "lesser evil' approach is logical, but it is imperative to administer the drug for at least 3 months to adequately assess its efficacy in a specific patient.