Bronchial challenge test are useful in diagnosis of bronchial hyperresponsiveness (BH). To assess the sensitivity of histamine test (HT) and exercise test (ET), 45 asthmatic patients (31 men, 14 women, ages 9-34) with normal resting pulmonary function test were studied. HT and ET were performed in two different days. HT was positive in 40 (6 severe, 23 moderate and 11 mild) and ET was positive in 13 (88.8% vr 28.8%, p < 0.001). All patients with positive ET had positive HT. There is a relationship between the degree of BH severity and the response to ET (chi 2 = 5.995; p < 0.05). The HT has a high profitability the diagnosis of BH. The ET has a low sensitivity.