These results were obtained on a double blinded study which compared the Nifedipine effects, a dihydropyrine calcium blocker of extensive cardiovascular function, the Ketotifen and a placebo orally administered, during 4 months, every 12 hours, on children with allergic asthma, older than 5 years old, who had a minimum of 2 years of evolution in their sickness. These people consulted the Allergic Service of the University Hospital of San Vicente de Paul in Medellín, Colombia, between July of 1984 and December 1986. Nifedipine diminished its intensity, frequency and the time the crisis lasted; it was seen at the end of the treatment. It also diminished bronchodilator consumption in more than 80% of the cases it 90% of the patients reported beneficial effects with Nifedipine and the improvement evaluated by the doctor showed 75%. These results were statistically similar to those obtained with Ketotifen but significantly superior to those obtained with the placebo. There wasn't any variation on the pulmonary function test, neither on the cardiovascular parameters evaluated. Side effects were mild and very few. We can assure that Nifedipine can be an alternative drug for the treatment of low or moderate child Extrinsic Asthma, given its similar behavior to Ketotifen, a drug of known effectiveness in this topic. The Calcium Blockers can become an elective treatment in the future for the asthmatic patient, if some molecules with higher affinity for respiratory tracts and better blocking effect, can be synthetized.