BACKGROUND: There are limited data describing lung function changes in children after an asthma exacerbation. Our hypothesis was that lung function does not fully recover in children in the months following an asthma exacerbation. METHODS: We used a dataset of children with asthma where lung function (including FEV1 , FEV1 /FVC ratio and FEF25-75 ) was measured at three-month intervals over a year. Mixed level models compared spirometry measured on two occasions three-months apart before a single exacerbation (assessments 1 and 2) to measurements made on two occasions after the exacerbation (assessments 3 and 4), with adjustment for covariates. Changes in spirometry over a year were also analysed across those with exacerbations in no, one or more than one three-month periods. RESULTS: For the 113 children who had a single exacerbation, spirometry measured made at assessment 1 or 2 did not differ at assessments 3 or 4 when the whole population was considered. When categorised into tertiles by change in %FEV1 between assessments 2 and 3, those with the greater reduction were more likely to be treated with long acting beta agonist, but in this category %FEV1 at assessment 4 had returned to the value at assessment 1. %FEV1 did not change over a 12month period within and between the three exacerbation categories (n=809). CONCLUSION: One or more asthma exacerbation was not associated with a fall in lung function for the whole population. Lung function does fall after an exacerbation in some individuals but after a period of months returns to pre-exacerbation values.