Tehran University of Medical Sciences Auditory and Vestibular Research 2423-480X 23 3 2017 07 31 22 29 Nahid Jalilevand Department of Speech therapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran Mohammad Kamali Department of Rehabilitation Management, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran Mahdiye Tavakoli Department of Speech therapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran Zohre Mahmudi Department of Speech therapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran Mansur Amiri Department of Speech therapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran Shahram Hadavi Department of Speech therapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran Mohanna Javanbaxt Department of Audiology, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran 2017 05 21 Background and Aim: During speech development in normal children, cluster reduction is one of the natural phonological processes. Children begin to produce some consonant clusters from the age of 2 years but ability to produce all consonant clusters continues up to 9. The main objective of this investigation was assessing the ability of Persian-speaking children in production of consonant clusters in mono-syllable CVCC words. Methods: In this cross-sectional and comparative study, production of 19 clusters with stop, fricative, affricate, nasal, and glide consonants in 38 words were tested in 200 Persian-speaking children at the age of 3 to 6 years in kindergartens of Tehran, Iran. Content validity indexes of 38 words were above 0.80 and Cronbach’s alpha of split half was 0.91. Results: More than 75% of 3-years-old children were able to produce /xl/, /bz/, /rs/, and /xm/ clusters. Age was positively correlated with correct production scores of words (p=0.001) and was negatively correlated with cluster reduction scores (p=0.001). Conclusion: Three-years-old normal Persian-speaking children may use cluster reduction in words with consonant clusters but this phonological process decreased by increasing of age; so, most of the 6-years-old children could produce consonant clusters correctly. Place of articulation more than manner of articulation affect on correct production of consonant clusters. https://avr.tums.ac.ir/index.php/avr/article/view/240