This paper reports the internal consistency and reproducibility of the Childhood Asthma Questionnaires, measures of quality of life and symptom distress in paediatric asthma. A total of 535 children aged 4-16 years completed age appropriate forms of the questionnaire, over 1- or 3-week intervals. Pearson correlation coefficients between 0.63 and 0.84 for subscales of the questionnaires indicated good test-retest reliability while intraclass correlation coefficients in a very similar range showed that scores also remained at the same level on the two occasions. Comparisons between children with asthma and healthy non-asthmatics indicate that these are likely to be true estimates of stability. Internal consistency varied widely but was higher for older children and longer subscales. Implications of the findings for the use of the questionnaires in the evaluation of new asthma treatments are discussed.