We investigated the content of cholesterol and phospholipids in the sarcotubular membranes from the rabbit fast-twitch muscle in various time intervals after the section of sciatic nerve. Along with the unchanged content of total phospholipids we found an increase of cholesterol in all investigated intervals. Significant elevation of cholesterol by about 33.8% following 14 days of denervation is associated with a three-times higher level of sphingomyelins. The elevated level of sphingomyelins persists after 28 days and the molar ratio cholesterol/phospholipids is 2.6 times higher in comparison with the control group. Investigation of cholesterol synthesis on muscle slices from the precursor 14C-mevalonic acid as well as of the activity of HMG-CoA reductase have shown that the cholesterol increase following denervation is not in correlation with its synthesis de novo. Similarly it has been shown that an increase of membrane cholesterol is not linked with the change of membrane fluidity (Tab. 3, Fig. 3, Ref. 30.)