Ketotifen is a sedative antihistamine promoted heavily for asthma treatment. Controlled trials are inconsistent: several did not find ketotifen better than placebo or cromoglycate. We do not have published controlled trials against inhaled steroids, the comparison most important to evaluate the efficacy of ketotifen. Ketotifen is poorly effective against exercise-induced asthma, and unable to reduce bronchial hyperactivity. The sedation and delay in therapeutic effect is also bothersome. Because of the uncertainties of its effect, ketotifen is not a first line drug against asthma, according to several international guidelines. Despite this information, ketotifen represented 17% of all antiasthmatic drug sales in Mexico in 1996, clearly exaggerated for the efficacy demonstrated. Ketotifen for asthma can be substituted with advantage by inhaled cromoglycate or corticosteroids. As a sedative antihistamine it is very expensive. The authorized publicity concerning ketotifen should be reevaluated with the current information available.