Signaling molecules play a critical role in the pathophysiology of airway diseases. Recent evidence shows that cyclic ADP-ribose (cADPr), an endogenous activator of the ryanodine receptor channel in mammalian cells, modulates agonist-induced calcium responses in airway smooth muscle (ASM) cells. In addition, cADPr-mediated calcium release appears to play an important role in the 'non-specific' increased ASM responsiveness to contractile agonists in cytokine-treated cells, a characteristic finding of asthma. Furthermore, other signaling molecules such as Rho/Rho kinase and phosphodiesterase also contribute to bronchial hyperresponsiveness. Thus, a better understanding of these signaling molecules that alter calcium signaling and contractility of ASM might provide new insight into novel therapeutic targets for the control of bronchial hyperresponsiveness.