Occupational voice disorders have been increasing for years. The aim of this study was to examine whether a constitutionally weak voice should be regarded as a risk factor for developing such voice disorders. In a prospective study, 15 female teacher students with a normal vocal constitution were compared with 18 students with constitutionally weak voices during teaching practice. There was a significant difference in the mean fundamental frequency of both groups after teaching for 30 min. Students with constitutionally weak voices tended to have increased values. Taking into consideration the physiological aspects of an increasing fundamental frequency as a sign of vocal fatigue, a constitutionally weak voice has to be regarded as a potential risk factor for developing a voice disorder in vocally intensive occupations. To prevent future vocal problems by appropriate prophylactic intervention (i.e. voice therapy, introduction to vocal hygiene), a phoniatric examination of vocal constitution and endurance is recommended at the beginning of a voice dependent professional career.