The authors have pointed out that phosphatidylcholine (PC) decomposition was accelerated in frozen carp ordinary muscle and that the acceleration was caused by dehydration of muscle accompanied with freezing. Since the dehydration of muscle would result in the concentration of components which might accelerate the PC decomposition, we studied the effects of the concentration of components on the acceleration of PC decomposition. Glycerylphosphorylcholine (GPC) productivity was measured at 37℃, for 10 h to evaluate the PC decomposition. GPC productivity was 2. 3 μmol/10 g of raw muscle for 50 %-dehydrated carp ordinary muscle which was minced and lyophilized, whereas it was scarcely detected for 55 %-dehydrated ordinary muscle prepared by centrifugation. GPC productivity of minced muscle only lyophilized to 55 % dehydration was almost equivalent to that of muscle, which was lyophilized to 50 % dehydration and then added with 2-fold concentrated fluid to regulate the water content to that of raw muscle, in spite of enrichment of enzyme and substrate. GPC productivity of minced muscle added with heated fluid was equal to that with water, this fact indicated that there might be no component in fluid to accelerate the GPC productivity. Addition of Ca^<2+>, Mg^<2+> and ovo protein to minced muscle did not result in the acceleration of GPC productivity, neither did the addition of NaCl to elevate the osmotic pressure. From these results, authors concluded that the acceleration of PC decomposition in frozen muscle was attributed not to the concentration of the components, but to some change in the arrangement of the enzyme, phospholipase A_2, and the substrate, PC.