Abstract: Transforming growth factor-1 (TGF-1) is a pleiotropic cytokine and is involved in the regulation of key events in development, disease, and tissue repair. Here we explored the expression of TGF-1 in zebrafish of which the full cDNA consists of 1571 bp and encodes 377aa. The sequence of this gene was obtained from NCBI. Phylogenetic analysis revealed that TGF-s were classified strictly with the same type of proteins. TGF-1 of zebrafish was classified on the same branch of the phylogenetic tree with TGF-1s of other fish. RT-PCR of this gene at different embryonic stages showed that TGF-1 existed in unfertilized eggs of zebrafish. The expression started to increase at 24hpf and maintained a high level until 72hpf. Whole-mount in situ hybridization (WISH) analysis showed that TGF-1 transcripts could be first detected in embryos at 24hpf and increased noticeably at later developmental stages. TGF-1 transcripts were mainly expressed in gill arches, lateral line primordium, otic vesicle, olfactory placode, heart and pronephros. These indicated that TGF-1 might play an essential role in immunoregulation, lateral line formation and vasculogenesis. Furthermore, the effect of hypoxia on the expression of TGF-1 in zebrafish embryogenesis was evaluated with RT-PCR, Real-Time PCR and WISH. After the hypoxia treatment the development of embryos was delayed and the expression of TGF-1 in embryos decreased dramatically. These results suggested that TGF-1 played an important role in zebrafish embryogenesis and might be related to the hypoxia-induced delay in zebrafish embryonic developement.