Using the sandwich enzyme-linked immunosorbent assay(ELISA)for grass carp growth hormone , plasma kinetics of rcGH in Clarias batrachus after administrations of rcGH were investigated .After intramuscular injections of rcGH (0 .2 and l μg g)into C .batrachus , the plasma rcGH levels were increased , peak values were seen at the end of 2 and 3 hours post-injection , and rcGH in plasma was undetected on the 2nd and 4th days post-injection , respectively .Similar uptake and clearance patterns were seen after intraperitoneal injections rcGH(0 .2 and l μg g)into C .batrachus . Intraperitoneal injections of rcGH (0 .5 , 1 and 2 μg g)to walking catfish , rcGH in plasma was all undetected on the 7th day post-injection .When rcGH(0 .2 and 0 .5 μg g)was injected into intracaudal vessel of C .batrachus , plasma rcGH levels decreased by way of exponential decay , rcGH in plasma was detectable 24h postintra-caudal vessel injection .