The study was undertaken to ascertain the speech defect of patients with malocclusion, especrally of poenbite patients, by means of the spectral analysis method. The expermental group was composed of ten female openbite patients and their mean age was 13.8 yrs. The control group was also composed of ten female girls ans then mean was 13.7 yrs. As for the speech materisl, eight Korean monphthrongs ans two Korean fricatives and two affricatives were used Speeches were recorded and then analyzed by a Kay 7800 drgital sonagraph. Formant frequency level or range was used as a phonemic parameter. The results were as follows. 1. Among Vowels /a/ F₁,F₃, and F₁/F₂ showed abnormahty /o/and/ω /F₂,F₂-F₁ and F₁/F₂ showed abonrmahty. 2. Among Consonants /s/and/h/ The upper and lower borders of the frequency range showed abnormahty. /ƒ/ The lower border of the ferquency range showed abonormahty. /C^h/ The upper and lower borders of the frequency range and concentration point showed abonormahty.