This work was aimed to study and evaluate the antihistamine activity (bronchodilation) for prepared series of 1,2,4-triazolo[1,5a]quinazolines. Screening of the bronchodilation activity of 1,2,4-riazoloquinazolines (1-27) was investigated in vitro using isolated thoracic tracheal rings of male guinea pigs pre-contracted with histamine. Screening procedure of bronchodilation test was performed in light to the standard reported method by examining the effects of the target molecules on isolated thoracic tracheal rings of male guinea pigs. The observed bronchodilation screening results are recorded and the potency (IC50) was determined in mM in comparison with theophylline as a reference drug. The tested triazoloquinazolines have exhibited promising antihistaminic activity against histamineinduced bronchospasm. Our findings have shown that compounds 2, 3, 11, 20 and 21 were found to possess the highest activity and could be useful as templates for further development through modification or derivatization to design more potent antihistamine.