Self-management plans are considered today an essential component of the management of asthma. The objective of the present study was (a) to explore patients' present practical knowledge of self-treatment of asthma, and (b) to provide an assessment of the effect of an educational program on this knowledge and self-treatment behaviour. Twenty four adults with asthma from the outpatient clinic of the Department of Pulmonary Medicine participated in a self-management program. They were provided with explanations on the symptoms and precipitating factors of their asthma, on its treatment with medication and their side-effects, and with personal written guidelines for self-adjustment of their medication. Prior to the program their practical knowledge of adequate self-treatment was investigated using a hypothetical scenario of a slow-onset asthma exacerbation. The effectiveness of the teaching and training program was evaluated by the change in knowledge prior to and 5 months after the program and self-reported behaviour of the participants at follow-up. (a) More than 60% of the patients lacked practical knowledge of self-treatment of a slow-onset exacerbation of asthma. (b) The educational program resulted in a significant increase (47%) of this knowledge. (c) Actual self-treatment behaviour, as recorded by the patients 5 months after completing the educational program, was adequate in only two of ten patients, who experienced an exacerbation during the study period. Many adults with asthma are deficient in practical knowledge of self-treatment of a slow-onset exacerbation. This knowledge was significantly augmented by an educational program. Nevertheless actual self-treatment behaviour at follow-up was inadequate in the majority of patients.