Vocal function of 28 patients following partial laryngectomy was studied with HGF-1 personal computer system. The system consists of spectrogram analysis of correlogram and sonogram. The result showed that different phonetic positions have different vocal functions. Vocal function of the patients who had new vocal cord and patients who received supraglottic hemilaryngectomy is nearly normal. Whereas vocal function of patients with supraglottic construction and speaking shunt is very poor. This system appears to be an objective and quantitative tool for vocal function study.