The vibratory behavior of 72 vocal folds with epithelial hyperplasia or dysplasia was investigated by means of videostroboscopy. The amplitude of vibration (AMP) and mucosal wave (WAV) were related to the relative area, depth, and relative volume of the lesion. The AMP and WAV were evaluated for the entire vocal fold (AMPE, WAVE) and for the affected portion or the lesion (AMPL, WAVL). The AMPE, AMPL, WAVE, and WAVL were negatively related to the relative area, depth, and relative volume. The relationship between the limited vibratory movement and the extent of the lesion was most significantly manifested in WAVL. A complete absence of any vibratory movement of the vocal fold took place only for large lesions occupying three fourths or more of the membranous vocal fold.