The aim of this study is to assess whether or not a correlative effect exist between the form of dental occlusion, and the speech performance efficiency level, the subjects were divided into groups A to F, A was subjects of normalocclusion, and no individual teeth abnormalities, B had the same occlusal pattern as A; but with individual teethAbnormalities, group C, Class II occlusion, with no individualteeth abnormalities Group D had the same occlusal pattern asC, but with individual teeth abnormalities, Group E with classIII occlusion and Group F had the same occlusal pattern butwith individual teeth abnormalities. The test buttery assessedthe intelligibility, and articulatory performance of the patients,whether or not nasal intonation of speech existed by simpletests, and nasoometer as well as visual viewing by the Nasalfiberscopy. Then speech laboratory measurements wereemployed to compare formant transition time & consonantduration in subjects. Conclusion: Class II occlusion have abetter performance than Class III, & both classes in addition toclass I subjects will have better performance in absence ofindividual tooth abnormalities, however most subjects areperceptually free from articulatory errors due to speechadaptive capacity.