The full-length cDNAs encoding alpha-class,rho1-class,rho2-class GST (GSTA,GSTR1,and GSTR2) were cloned and sequenced from the blue tilapia (Oreochromisco aureus),and the GSTR1,GSTR2 were cloned and sequenced from the Nile tilapia (Oreochromis nilotica) by RT-PCR and RACE method.The full-length blue tilapia GSTA cDNA was 933 bp in length,containing an open reading frame of 669 bp (encoding 222 amino acids),flanked by 98 bp 5′UTR and 166 bp 3′UTR.Both the blue tilapia and Nile tilapia GSTR1 cDNA ORF were 681 bp (encoding 226 amino acids),and both the blue tilapia and Nile tilapia GSTR2 cDNA ORF were 693 bp (encoding 230 amino acids),respectively.Homology and the phylogenetic tree constructed based on GST sequences showed that the tilapia GSTs amino acid sequence were highly conserved with fish,and had low homologous relationship with amphibian,bird and mammal GSTs.