We investigated the pulmonary function of male asthmatics with childhood-onset asthma. Our results revealed that adult asthmatics with mild symptoms apparently have abnormal pulmonary function. On the other hand, after a 3-6-month symptom-free period, and even after inhalation of bronchodilator, they still showed significant residual abnormalities in pulmonary function. Pulmonary function tests are very sensitive tools for the assessment of airway limitations during an acute asthmatic attack. However, these tests are not sensitive enough to detect residual abnormalities in asymptomatic asthmatics. Although the positive predictive rate for detecting small airway dysfunction in asymptomatic asthmatics is not high, FEF25-75 proved to be the best (63.2%) among the conventional pulmonary function parameters. We therefore suggest using FEF25-75 instead of FEV1 or peak flow rate in clinical practice for the conventional assessment of effectiveness of treatment, especially in the follow-up of asthmatic patients. More sensitive and simple tests are required in the future for detection of small airway dysfunction in asymptomatic asthmatics. Moreover, strict and early treatment of this abnormality with steroids is mandatory to prevent the formation of sequelae.