OBJECTIVE: To determine whether asthma knowledge of caregivers could improve health outcomes in pediatric patients. METHODS: The study design was a prospective randomized controlled trial in asthma patients aged less than 12 years-old. The study was carried out in asthma clinic at Queen Sirikit National Institute of Child Health, Bangkok, Thailand between August 2002 and March 2003. Eleven active and 11 control patients were invited to attend a clinic. At the clinic the pharmacists conducted interviews and asked all caregivers to answer a questionnaire containing 18 true-false questions regarding asthma knowledge. After completing the questionnaire, pharmacists provided knowledge of asthma regarding treatment and environmental care to caregivers in the intervention group. During the study period, patients in both groups continued to receive the usual care from their physicians. Patients and caregivers were followed up during the next six months and the same process was repeated. The outcome measure was the rate of hospitalization in asthma patient between groups. RESULTS: At baseline there are no significant differences in asthma knowledge between intervention and control group. At the end of study, the intervention group is generally better at answering the asthma questions correctly. The number of hospitalization in the intervention group decreases from 31 to 13 (p<0.05), whereas there is no statistically significant difference in the control group. CONCLUSIONS: The present work suggests that pharmacist's involvement in asthma clinic has increased caregivers' knowledge leading to a decrease in the number of hospitalization. However, further training is required for caregivers to optimize their role in helping asthma patients. Further work could be carried out to determine whether the results of this study are reflective of the knowledge in adult patients.