At present, there are a lot of drugs for the therapeutic approach of all the severity levels of asthma in developed countries. However, there are big difficulties in the correct use of inhalation devices, and usually there are drug related problems causing poorly controlled asthma. The objective of the study is to prove if the community-based pharmaceutical care service improves health outcomes in patients with asthma. Community intervention trial, with a controlled multicenter quasi-experimental design, measuring the response variables before and after an observation period of 9 months. 96 patients were recruited in the Intervention group and 69 in the Control group, in 37 pharmacies. The measurement instruments used were the specific quality of life questionnaires AQLQ (adults) and PAQLQ (pediatric) of Juniper, and initial and final interviews containing a scale of 10 signs of poorly controlled asthma and data about health services utilization. Quality of life measures in the Intervention group achieved a mean increase of 0.82 points in adults and 0.81 in children, both clinically significant because they exceed the established clinical thresholds (0.5 and 0.42 respectively). Also there was a statistically significant difference in the final comparason between groups. The signs of poorly controlled asthma decreased significantly in the Intervention group from an initial mean of 2.72 into 1.15. Also a significant difference was found in the final comparason between groups. The community-based pharmaceutical care service had a beneficial effect in health related quality of life in asthma patients, and in the signs of poorly controlled asthma. It was not found a significant improvement in health services utilization.