Leukotrienes (LT) are synthesized from arachidonic acid by several enzymes such as phospholipase A2, 5-lipoxygenase, LTC4 synthase, as a consequence of a wide range of inflammatory stimuli. Leukotrienes seem to play a pivotal role in the maintenance of the inflammatory processes as they exert numerous biological activities, i.e. chemotactic action on polymorphonuclear cells, bronchospastic action, vasodilator and secretagogue effects. Thus, the inhibition of LT activity may result in antiinflammatory action. Several compounds capable of blocking either LT synthesis or LT receptors have recently been developed and clinically tested in different experimental models. In particular, encouraging results have been obtained in the asthma model, but interesting clinical observations have also been performed in psoriasis, ulcerative colitis and rheumatoid arthritis. Although further studies and optimization of this kind of treatment are required, a possible clinical role of LT antagonists as antiinflammatory therapy for selected diseases may be envisaged.