en Speech Therapy Speech Therapy Original Research Original Research <p><strong>Background: </strong>Developmental Sentence Scoring (DSS) was developed as a numerical measurement and a clinical method based on the morphosyntactic acquisition in the English language. The aim of this study was to develop a new numerical tool similar to DSS to assess the morphosyntactic abilities in Persian-speaking children.</p> <p><strong>&nbsp; Methods:</strong>&nbsp; In this cross-sectional and comparative study, the language samples of 115 typically developing Persian-speaking children aged 30 - 65 months were audio recorded during the free play and picture description sessions. The Persian Developmental Sentence Score (PDSS) and the Mean Length of Utterance (MLU) were calculated. Pearson correlation and one &ndash; way Analysis of variance (ANOVA) were used for data analysis.</p> <p><strong>&nbsp; Results:</strong> The correlation between PDSS and MLU in morphemes (convergent validity) was significant with a correlation coefficient of 0.97 (p< 0.001). The value Cronbach&#39;s Alpha (a= 0.79) in the grammatical categories and the split-half coefficient (0.86) indicated acceptable internal consistency reliability.</p> <p><strong>&nbsp; Conclusion:</strong> The PDSS could be used as a reliable numerical measurement to estimate the syntactic development in Persian-speaking children.</p> <p></p> Language Measurement, Validity, Reliability, Typically Developing Children, Persian Language. 980 989 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-1068&slc_lang=en&sid=1 Nahid Jalilevand jalilevand.n@iums.ac.ir 200319475328460025236 200319475328460025236 No Department of Speech and Language Pathology, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran. Mohammad Kamali kamali.mo@iums.ac.ir 200319475328460025237 200319475328460025237 Yes Department of Rehabilitation Management, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran. Yahya Modarresi ymodarresi@yahoo.com 200319475328460025238 200319475328460025238 No Department of Linguistics, Institute for Humanities and Cultural Studies, Tehran, Iran. Yalda Kazemi y.kazemi@hotmail.com 200319475328460025239 200319475328460025239 No Department of Speech Therapy, Faculty of Rehabilitation, Isfahan University of Medical Sciences, Isfahan, Iran.