BACKGROUND. After treatment for early glottic carcinoma, a considerable number of patients end up with voice problems that interfere with daily life activities. The objective of this randomized and controlled study was to assess the efficacy of voice therapy in these patients. METHODS. Of 177 patients, 6-120 months after treatment for early glottic carcinoma, 70 patients (40%) suffered from voice impairment based on a 5-item screening questionnaire. Approximately 60% of those 70 patients were not interested in participating in the current study. Twenty-three patients who were willing to participate were assigned randomly either to a voice therapy group (n = 12 patients) or to a control group (n = 11 patients). Multidimensional voice analyses (the self-reported Voice Handicap Index [VHI], acoustic and perceptual voice quality analysis, videolaryngostroboscopy, and the Voice Range Profile) were conducted twice: before and after voice therapy or with 3 months in between for the control group. RESULTS. Statistical analyses of the difference in scores (postmeasurement minus premeasurement) showed significant voice improvement after voice therapy on the total VHI score, percent jitter, and noise-to-harmonics ratio in the voice signal and on the perceptual rating of vocal fry. CONCLUSIONS. Voice therapy proved to be effective in patients who had voice problems after treatment for early glottic carcinoma. Improvement not only was noticed by the patients (VHI) but also was confirmed by objective voice parameters.