This study mainly investigated the growth replacement of hypophsectomy of crucian carp by human growth hormone (hGH) and that of F2 transgenic mirror carp by corresponding transgene. The survial rates of hypophysectomized crucian carp (Carrassius auratus L.) and mirror carp (Cyprinus carpio) were also studied. A preliminary analysis was made on the biological functions of GH by measuring several plasma constituents of hypophysectomized crucian carp. The results are as follows: (1) The linear growth of both crucian carp and mirror carp stopped after hypophysectomy, revealing the importment roles of hypophysis in fish growth. (2) The hypophysectomized crucian carp resumed its linear growth after injecting hGH (2ug/g body weight/10 day). It was proved that hGH could partly replace the actions of hypophysis and accelerated the growth of crucian carp. (3) The foreign hGH gene was steadily intergrated in various tissues and organs of F2 transgenic mirror carp. The linear growth was highly significant of hypophysectomized F2 mirror carp carrying hGH gene. The special growth effect demonstrated that the foreign hGH gene could be expressed in F2 and that the expressed product could partly replace the actions of the hypophysis and accelerate the growth of the hypophysectomized F2 mirror carp. (4)Hypophysectomy decreased the survial rates of crucian carp and mirror carp. The survial rates of hypophysectomized erucian carp and mirror carp raised at high temperature (25 ℃) were lower than those at low temperature (15 ℃). The survial rate of hypophysectomized mirrrr carp was lower than that of hypophysectomized crucian carp. (5) The blood glucose level of hypophysectomized crucian carp was higher than that of sham- operated crucian carp after operation, which was the stimulating response on hypophysectomy. We did not find differences in plasma protein and cholesterol between the hypophysectomized and the sham-operated crucian carp. The total plasma free fatty acids (PFFA) and the total plasma free amino acids (PFAA) decreased after hypophysectomy. Injection of hGH in the hypophysectomized crucian carp further decreased the PFAA level but did not affect the PFFA level.