There is no arguing about the importance of voice, especially in groups of vocal professional voices. The question is what characterizes, the most, normal or pathological voice in relation to aspects of human working life. Harmonics to noise ratio, according to findings from the field of voice disorders, is the most representative method to differ normal from pathological voice. In this research significant differences were found in harmonics to noise ratio in relation to the length of the working age of 29 teachers of primary schools in Zagreb. Teachers with the longest working age (40-yr.) showed the most distorted voices. The best quality of voice with great ratio of harmonics to noise was found in the group of teachers with 10 years of professional work. Acoustical analyses were made by ezvoiceplusTM version 2.0 and Gram. 2.3. Significant statistical differences were established by the T test of Statistica for Windows, version 4.5. [Work supported by Ministry of Science and Technology of Republic of Croatia.]