A new beta 2-agonists, broxaterol, administered by oral spray has been tested to evaluate its action modifying on the bronchial hyperreactivity to metacholine. Such drug has been administered double blind Vs salbutamol individualizing for both, at 15' and 90' premedication the PD20 FEV1 (doses of metacholine necessary to reduce of 20% the FEV1). The results that we have obtained confirm the protective capacity for both drugs on the bronchoconstriction induced by aspecific stimulus. However, in confront with salbutamol, the broxaterol presents an action more lasting in the time. Such requisite and absence of collateral effects permit to affirm that this new beta 2-agonists is fit for its utilization in the infantile intrinsic asthma.