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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.