The amplitudes of sustained vowels were measured at the dominant amplitude peak of each fundamental period of the acoustic signal picked up by a microphone coupled to the pretracheal skin. Serial correlation coefficients were computed and correlograms were made for each sample to investigate the periodicity in the modulation of the amplitude. Three groups of subjects were studied: 15 cases with laryngeal neoplasms, six cases with unilateral laryngeal paralysis, and 20 normal subjects as a control group. In each group of subjects, a high correlation was often found between the consecutive dominant amplitude peaks. The correlograms for patients with laryngeal neoplasms often displayed strong periodicities with periods of three to 12 fundamental periods, while for the paralysis cases no evidence of periodic modulations in the same range was found. The results seem to indicate that amplitude information may be useful for the development of an objective measure to evaluate laryngeal dysfunction and to detect some pathologies in the larynx.