OBJECTIVE To investigate how parents use bronchodilator treatment for relief of symptoms when treating their asthmatic preschool children. METHODS A commercial electromechanical timer device was attached to a large volume spacer to record the time and date of each use of inhaled bronchodilator over two months. The recorded time and dates were compared with symptoms noted in an asthma diary card. METHODS Large paediatric teaching hospital in Glasgow. METHODS 29 preschool children with moderately severe asthma attending a specialist paediatric asthma clinic. METHODS Inhaler use measured by the timer device; symptoms and inhaler use recorded by parents in a daily asthma diary. RESULTS Satisfactory data were obtained in 22 of the 29 children; the median number of study days was 53 (range 18-77). Asthmatic symptoms were recorded on a median of 30 (3-77) days. Bronchodilator was used on a median of 19 (2-73) days, or on 63% (7-100%) of days when symptoms occurred. The median number of puffs used in a day was 1 (range 0-100) and was significantly related to symptom severity in only 14 of the 22 children. In only two of the 22 children was bronchodilator given more frequently than four hourly, and only five children ever used more than 12 puffs a day. CONCLUSIONS The frequency of parental administration of bronchodilator treatment was variable and not closely related to the parent's record of symptom severity. Parents often recorded symptoms in their children but did not treat them.