Asthma control, defined by asthma symptoms and lung function, and asthma medication use, was assessed in 123 adolescent asthmatics. Sputum eosinophilia (>or= 2.5% eosinophils) and bronchial hyperresponsiveness (BHR) to hypertonic saline were also measured to assess whether these additional objective parameters might aid in determining asthma control; 54.5% of subjects had adequately controlled asthma; 50.4% of all subjects reported inhaled corticosteroid use in the preceding 12 months; however, only 22.3% reported regular use. Although BHR and median eosinophil numbers were significantly higher in the inadequately controlled asthmatics, BHR and sputum eosinophilia had poor sensitivity for detecting inadequate asthma control.