With every deep inspiration (DI) or sigh the airway wall stretches, as do the airway smooth muscle cells that it contains. In response, the airway smooth muscle (ASM) cell undergoes rapid stretch-induced cytoskeletal fluidization. As a molecular mechanism underlying that ASM fluidization response, here we demonstrate a key role for the actin-severing protein, cofilin. Using primary human ASM cells, we simulated a DI by imposing a transient stretch of physiologic magnitude and duration. We measured the resulting changes in contractile forces using traction microscopy. After a transient stretch, cofilin knock-down cells exhibited a 29{plus minus}5% decrease in contractile force compared to pre-stretch conditions. By contrast, control cells exhibited a 67{plus minus}6% (p< 0.05) decrease. Consistent with these contractile force changes, actin filaments in cofilin-knockdown cells remained largely intact, whereas actin filaments in control cells were rapidly disrupted by transient stretch. In addition, we found that, compared with control cells, cofilin knockdown cells had a higher contractile force at baseline, and a slower rate of remodeling post stretch. Furthermore, the severing action of cofilin was restricted to the release phase of the transient stretch. We conclude that the actin-severing activity of cofilin is an important factor in stretch-induced cytoskeletal fluidization, and the resulting bronchodilatory effects of a DI.