The ontogenses of eight isozymic systems in the developing blunt-snout bream, Megalobrama amblycephala, were analyzed with regard to morphological stages of embryos. The isozymic patterns of eight isozymic systems, Lactate dehydrogenase (LDH), Malate dehydrogenase (MDH), Glutamate dehydrogenase (GDH), Glucose-6-phosphate dehydrogenase (G6PD), Alcohol dehydrogenase (ADH), Isocitrate dehydrogenase (IDH), Esterase (EST) and Alkaline phosphase (AKP) in the early embryonic stages (0-105 hr after fertilization) and six adult tissues of the blunt-snout bream, were resolved by vertical starch-gel electrophoresis. Approximately 23 gene loci which encoded these isozymes expressed in the embryonic stages and adult tissuse of the blunt-snout bream. Most isozymes investigated in the blunt-snout bream ontogenesis might be distinguished into three types with regard to expressing models: Those enzymes present in fairly constant activies in developing embryos tended to be universal or almost universal present in almost all adult tissaes and organs, such as LDH-B_4, LDH-A_1B_3 and EST-5; The 2nd type enzymes appeared in the end or later stages of embryogenesis were specific in the differentiated adult tissuse or organs, closely correlated with the morphological or functional defferentiation of these particular tissues or orgens, such as LDH-C_4 and IDH; The third was an "embryo-specific" isozymic from of EST-1 and E-MDH, latter to be "stage-specific" at same time. In addition; the changes of activities in MDHs as well as between them and G6PD exhibited some coincidence which seemed to be of coordinate control. Different from the general result of many fishes, the GDH enzyme pattern of the blunt-snout bream was observed throughout entire embryonic stages, it had no tissue specificity in the adult tissues. lastly, in the present paper, the changes of activity in several essential isozymes were discussed in relatie onshaps with metabolid activities of the embryonic development. It was clear that the exactness of time-space effect in the gene control systems was an essential prequisite for ensuring normal metabolic activities in the blunt-snout bream ontogenesis.