Ultra-high speed motion picture laryngeal photography was employed on four subjects to determine the possible effects on the behavior of the internal larynx of orally administered topical anesthesia. Various parameters of laryngeal behavior were investigated, with and without anesthesia, and compared. They included maximum glottal width, glottal length, width of glottis spuria, duration of opening, closing, and closed phases of the vibratory cycle, and glottal area as a function of time. Results were consistent and failed to demonstrate that application of topical anesthesia affects the behavior of the larynx. © 1969 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.