The results are reported of a preliminary study to a controlled trial evaluating health education in asthma. A questionnaire designed to assess asthma morbidity in the previous twelve months and knowledge of the condition was administered to 50 asthma patients. An independent assessment of morbidity was made by the patient's general practitioners, utilizing case notes and their knowledge of the patients. For each aspect of morbidity, `severe' asthma as assessed by doctors tended to be associated with increasing disability on questionnaire assessment. Overall, questionnaire `morbidity scores' were significantly higher in the doctors' `severe' group. Patients' level of knowledge was low, but no significant correlation was found between patients' level of knowledge and level of morbidity.The findings suggest that there is a need for health education in asthma, and that the questionnaire used is a valid tool for measuring the impact of such education on patients' morbidity. An outline of the controlled trial for evaluation of health education is given.