Insulin like growth factor I (IGF-I) regulates growth, protein synthesis, and cell proliferation and differentiation in vertebrates. Polymorphisms of insulin-like growth factor-1 (IGF-1) gene transcript alleles of 3 different breeds of chicken (Sasso as a native breed, Arbor Acres plus and Cobb 500) were assessed. The associations of these polymorphisms with growth rate of the studied breeds were also evaluated. Total RNA were isolated from Chicken livers and IGF-1 gene was amplified from each breed by RT-PCR using specific primers flanking a certain region of the gene. The amplified products were then subjected to SSCP analysis for genotype identification. Three different banding patterns were obtained for the three breeds with a unique pattern for the Cobb 500 (the fastest growing breed). In this report, we describe how SSCP analysis of RT-PCR products can be used to evaluate the transcript expression pattern of avian IGF-1 polymorphism and their effect on the growth traits of chickens.