A 10-year-old patient with asthma, diagnosed in early childhood, with a pre-bronchodilator forced expiratory volume in 1 second (FEV1) of 75% of predicted attends a routine follow-up visit. The patient and family perceive his asthma as 'well controlled', but should his physician be concerned about his reduced lung function? What are the implications of a lower than expected FEV1 in childhood on the respiratory health of this patient in adulthood? Lung function is known to track with age, and there is a high likelihood that this patient will enter adulthood with a sub-optimal lung function.