In this review we went through eight placebo-controlled clinical trials of the folic acid antagonist methotrexate in the treatment of bronchial asthma. The studies, which differ in their methods and findings, are reviewed critically. Some studies seem to give documentation of methotrexate as an effective drug in reducing the corticosteroid requirements in patients with chronic corticosteroid-dependent asthma. Adverse effects are wellknown from the use of methotrexate in patients with rheumatoid arthritis and include nausea, diarrhoea, vomiting, transient increases in liver enzymes, alopecia and stomatitis. Rare but potentially life-threatening adverse effects are interstitial pneumonitis, opportunistic infections, bone marrow- and renal insufficiency. The role of methotrexate in patients with chronic corticosteroid-dependent asthma still needs to be clarified. Practical guide-lines in treating asthma patients with methotrexate are suggested.