There have been no estimates of the actual cost of asthma care to Australian families. Previous estimates have been of the total cost to the community and have relied upon data collected by government departments and agencies. It was the aim of this investigation to estimate the cost of childhood asthma from the parents perspective in Australian families. A total of 238 asthmatic children aged 8-12 years were identified through prevalence studies of asthma in Sydney and Belmont, N.S.W. Children were selected if they had wheezed in the previous 12 months, had used asthma medicines or had airway hyperresponsiveness when tested. The study sample had a wide range of asthma severity. Data were collected retrospectively and prospectively. Parents completed a questionnaire which asked about health insurance and special asthma equipment costs in the previous 12 months. Every 2 weeks for a total of 3 months between February and June parents completed further questionnaires which assessed costs incurred because of their child's asthma, together with time spent obtaining treatment. Items included doctor consultations and tests, alternative practitioner consultations and tests, medications and alternative therapies purchased, hospital and ambulance use, and the cost of childcare as a consequence of asthma. We collected two or more months of prospective data from a total of 193 children. The mean annual cost of asthma to the family was A$212.48 per asthmatic child and 13.4 hr were spent obtaining treatment. For the group of children who had not visited a doctor in the previous year, the mean annual cost was A$85.60 and 13.1 hr were spent obtaining treatment.(ABSTRACT TRUNCATED AT 250 WORDS)