Objective: Primary IGF1 deficiency (IGFD) is defined by low levels of IGF1 without a concomitant impairment in GH secretion in the absence of secondary cause. The aim of this study was to evaluate the prevalence of non-GH deficient IGFD in children with idiopathic short stature (ISS) with anthropometric assessment of these children. Subject and methods: The study included 50 children with idiopathic short stature following up at Diabetes Endocrine and Metabolic Pediatric Unit at Cairo University Pediatric Hospital during the period from February/2010 to May/2011. Children were included based on the following criteria: i) SS with current height SDS≤ –2.5, ii) age between (2-9) years in boys and (2-8) years in girls, and iii) prepubertal status. Exclusion criteria were: i) identified cause of SS and ii) pubertal children. IGF1-deficient children were defined as children without GH deficiency and with IGF1 levels below 2.5 th percentile. Results: Among 50 children with ISS, 14 (28%) had low IGF1 levels, consistent with a diagnosis of primary IGFD. When compared with non-IGFD children, IGFD children had lower birth weight SDS (–1.8 vs –0.7 SDS, P<0.0001) and lower height SDS (–4.2 vs –3.1 SDS, P<0.05) and more delayed bone age (2.6 vs 1.6 years, P=0.001). Conclusion: 28% of undiagnosed idiopathic short stature children presented with primary IGF-1 deficiency in this study which confirmed the major independent role of IGF-1 on bone growth and development