Abstract: By use of starch or polyacrylamide gel electrophoresis the patterns of expression of six isozymic systems (LDH, MDH, IDH, ADH, SDH and EST) were investigated in six differentiated adult tissues (brain, eye, heart, kidney, muscle and liver) and the early developmental stages (from unfertilized egg to the complete absorption of yolk) of bighead carp. Isozyme genes in adult bighead carp apparently exhibit a tissue-specific expression. During the early developmental stages, both ADH and SDH genes seem to be inactive; EST isozymes are present but exhibit no evident developmental change; LDH, MDH and IDH isozymes have different patterns of ontogenetic change. In comparison with those in grass carp and silver carp, the expression of Ldh-A gene in bighead carp is delayed during its ontogenesis. The above results provide basic information for the biochemical genetic survey of bighead carp populations and artificial breeding of bighead carp.