The insulin-like growth factor-I receptor (IGF-R) is an important component of the insulin-like growth factor system, which plays a key role in embryonic growth, formation of the nervous system, skeletal muscle development, and also appears to contribute to the establishment and progression of tumors. Despite its importance, little is known about the tissue distribution and expression pattern of during embryonic development in most commercially important cultured fish species. We isolated a 5 741 bp full-length cDNA from grass carp( cDNA included an 822 bp complete 5′ untranslated region (5′UTR), a 581 bp 3′UTR, and a 4 338 bp open reading frame (ORF) region which encoded a 1 445 amino acid protein. The mature peptide contained seven structural domains including two Recep-L-domains, one Furin-like domain, three FN3 domains, and one PTKc-IGF-1R domain. Among these, the PTKc-IGF-1R domain was the most conservative domain of IGF-R may play different transductional roles among different teleost species. The ORF deduced from the cDNA sequence was 95%, 93%, and 66% identical to the corresponding regions of IGF-R, respectively, indicating a high level of conservation of IGF-R has a high amino acid sequence identity with common carp and zebrafish IGF-IGF- mRNA was detected during embryogenesis, beginning at 16 hpf (hours post fertilization) and continuing through the larval stages. The mRNA was transcribed in almost all adult tissues except the intestine, with expression being highest in the grass carp heart. Using whole mount mRNA was detected ubiquitously in 16 hpf embryos, with strong signals in the brain and spinal cord, but only a weak signal in the tail-fin. In 24 hpf embryos, the mRNA signal was strong in brain, spinal cord, and in rapidly growing regions such as tail-fin tip. Our results provide insight into the IGF-R signaling pathways and provide a basis for future genetic breeding of grass carp.