The effects of chronic posterior cricoarytenoid muscle denervation were assessed at 3 and 7 months in 26 animals following resection of 10 cm of recurrent laryngeal nerve with stump ligation. The physiology of denervation was characterized by a decrease in contraction strength and an increase in contraction time. The reduction in contraction strength reflected the loss in muscle weight and atrophic changes in fiber density and diameter. A change in muscle composition occurred because of the increased susceptibility of fast-twitch (type 2) fibers to degeneration. However, the compositional change alone could not account for the slowing of muscle contraction. Muscle fibrosis was negligible at 3 months, but encompassed one third of the fiber population by 7 months. In view of the irreversible nature of fibrosis, this study suggested that clinical intervention to rescue denervated posterior cricoarytenoid muscle fibers should be delayed no longer than 7 months to improve the chances for full recovery.