The growing use of guidelines to manage asthmatic patients prompted us to evaluate their impact on clinical practice. This study was performed in two similar groups of asthmatic patients. A retrospective and prospective review of medical records in an asthmatic population was performed. The patients were followed up for a mean period of 2 years before (group 1 [G1]) and after the publication of the Guideline for Asthma Treatment (group 2 [G2]). After evaluation of objective/clinical measurements we noticed a significant difference between both groups. There were 23 and 40 patients who did not complain of any respiratory symptoms in G1 and G2, respectively. The total number of visits to the emergency department decreased by more than 75%, from 26 (G1) to six (G2). The forced expiratory volume in 1 sec improved by a mean of 4% in G1 and 9% in G2. After application of the guidelines there was a redistribution of the degree of disease severity. In G2, there was a 12% increase in the use of long-acting beta2-stimulating sprays; 40% of the patients were using a combination of a long-acting beta2-stimulating drug and an inhaled steroid. In our experience, the use of the Global Initiative for Asthma (GINA) guidelines leads to better management of asthma patients with different degrees of severity. These findings suggest the need to perform a similar analysis in a broader setting such as a national multicenter survey in order to collect information on the challenges of putting these theoretical difficulties into practice and to compare their implementation in distinct centers.