The aim of this study was the investigation of bronchial reactivity in human bronchial smooth muscle in vitro. In fact, the study has two purposes: to achieve the best methods of research on human bronchial strips reactivity in vitro; to reveal the effect of acetylcholine and histamine on bronchial smooth muscle; The contractile effect of acetylcholine appears at 10(-6) M in the organ-bath; the maximal acetylcholine contraction was obtained at 10(-3) M in the organ-bath. Histamine induced a maximal contraction at 10(-3) M, but a concentration of 10(-3) M in the organ bath had no effect.