The effect of various concentrations of sucrose on the quality change of lyophilized myofibrils during storage was examined. Myofibrils from live carp, Cyprinus carpio, were ground with polyphosphates and sucrose. The mixtures were freeze-dried at 35°C, ground into powder, packed in 0.1mm thick polyethylene bags, and stored for 6 months at 20°C. At suitable intervals, aliquots of the mixtures were taken out and examined as to quality, using as indexes the solubility in 0.6M KCl, the relative viscosity, and the ATPase activity of the 0.6M KCl extractable prolein, and the total ATPase activity. The higher the concentration of sucrose, the better was the quality retention of the powder. Above 5 per cent in a wet basis before freeze-drying, however, there was no sig-nificant difference in the effect of sucrose. It was also noted that protein denaturation was accelerated in the powder to which but polyphosphates had been added.