Objective: Early Diagnosis and intervention of primary stuttering is the key for prevention of chronic developmental stuttering. Normal nonfluency of children under 5 years old is an important differential diagnosis of primary stuttering. The goals of this research are finding accuracy of diagnoses on children referred to Saba speech therapy Clinic labeled as normal nonfluency and introducing move precise methods of differential diagnosis. 

Materials & Methods: The research method is case series study in which through simple sampling procedure stuttering children referring to SabA Clinic during 1382 & 83 were studied. 10. Research tools and data collection consist of: questionnair, spontaneous speech sample recording and determining VOT using laryngograph processor. It should be noted that because normative date of stutteres VOT the lack of the normal subjects VOT are analysed and comared with stutterers.

Results: Based on numerical criteria, our findings indicate that only one of stutterers was normal nonfluent and the others were stutteres. VOT data of stutteres also were compared to that of normal matched children. The results revealed that all of stutterers had significantly (P<0.05) longer VOT than normal subjects .

Conclusion: This study provides a good numeric and clinical index for speech language pathologists for diagnosis of primary stuttering and normal nonfluency. Morover,. using VOT would help accurate diagnosis.