The nerve supply of the human interarytenoid (IA) muscle has been controversial for more than a century. In this study the contribution of the recurrent and superior laryngeal nerves to the IA was investigated in 10 adult human larynges. The larynges were obtained from autopsies and processed with the modified Sihler's technique which clears soft tissue while staining nerve. The IA muscles were dissected off the specimens and transilluminated to demonstrate their nerve supply. The results demonstrated that all 10 IA muscles were bilaterally innervated by both recurrent laryngeal nerves (RLNs) as well as branches of both superior laryngeal nerves (SLNs). These nerves combined within the IA muscles to form a dense anastomotic plexus which was highly variable between specimens. The exact nature of the internal SLN neurons, whether motor or sensory, their innervation targets, or their function, were not discernible. Additional anatomic findings were the presence of large neural communications directly between the SLN and RLN, and smaller neural connections from side to side. All of these results disagree with currently accepted descriptions of laryngeal neuroanatomy.