We studied the relationship between patient-pharmacist communication and asthma treatment, including patient understanding of drug therapy, ability to self-treat with inhaled drugs, and control over asthma. The study was among adult patients who had received inhaled steroidal or other drugs from community pharmacies in Hokkaido, Ibaragi, Tochigi, Kanagawa, and Osaka prefectures for at least one year. During the month of November 2007, pharmacists explained the study to patients and obtain consent before distributing questionnaires to be filled out and mailed back. Survey items covered the nature/extent of the pharmacist's explanation, the patient's degree of understanding, frequency of inhaled steroid use, frequency of asthma attacks, degree of improvement with inhaler use, skill in using inhaled drugs, and self-evaluation of communication with the pharmacist. Analysis was carried out using the 114 valid data sets obtained. The ratio of men to women was 4: 6, and the average age was 61.8 years. Compared with patients citing communication problems with pharmacists, those who had good communication received significantly higher scores in terms of understanding the purpose of inhalers, drug interactions, and side effects, and coping with attacks, as well as in indices of skill in using inhaled drugs. The degree of improvement in asthma attacks was also significantly higher among patients with self-evaluation of good communication with pharmacists. We suggest that communication between patient and pharmacist is associated with understanding of pharmacotherapy, as well as their ability to use inhaled medications and gaining good control over their asthma.