An isolation procedure for rat brain aldolase C has been developed which also permits the isolation of aldolase C from experimental hepatomas.Certain enzymatic properties (specific activity and Michaelis constant towards the two specific substrates : fructose 1,6-bisphosphate and fructose 1 -phosphate) and physico-chemical properties (molecular weight, N-terminal amino-acid) of the two enzymes have been studied and compared. Moreover, an amino-acid analysis has been carried out for rat brain aldolase C.Within experimental errors, the two enzymes appear to be identical.