B2-agonists play a first-rate role in the exercise induced asthma (EIA) prevention for their capacity to modulate the bronchial tone. We studied the efficacy of a new B-sympathomimetic (Broxaterol) in 10 children (7 males and 3 females) with EIA in double blind vs salbutamol. During two consecutive days a basal treadmill incremental exercise test was made for determining bronchoconstriction rate (IB). Subsequently the test was repeated 30' and 150' after the drug's administration. The Broxaterol premedication determined, by comparison with the basal IB value, a mean difference of 11.9 after 30' (p less than 0.05) and 10.0 after 150' (p less than 0.01). No significant correlation was found comparing the salbutamol premedication. In conclusion our data confirms the Broxaterol efficacy in exercise-induced asthma prevention.