In this study, associations between classroom conditions and teachers' voce use were researched (N=40). Acoustic variables were reverberation time (T-60), early decay time (EDT), sound strength (G), the ratio of early and late sound energy arriving to a listener (C-50), the ratio of early arriving sound energy to overall sound energy (D-50), speech transmission index (STI) and rate of spatial decay of sound pressure levels (DL2). Indoor climate was also evaluated. Voice variables measured were sound pressure level (SPL), fundamental frequency (F-0) and spectrum slope. According to findings when the values of T-60, EDT and DL2 were lower or the values of C50, D50 and G higher, teachers' voice SPL was higher. When reverberation times were longer, F-0 increased and when the values of C-50 and D-50 were higher, men's F-0 was higher. Poor indoor air increased occurrence of laryngitis. The results showed that indoor environment affects voice use and thus, is associated with the health of voice organs.