The phospholipid composition of rat gastrocnemius muscles was assessed one to nine days after sciatic nerve transection was performed either close to the muscle (5-8 mm from the point of entrance of the nerve into the muscle for short-stump nerve sections) or far from it (30-35 mm central to the nerve's point of entrance for long-stump nerve sections). In both instances, denervation did not cause striking changes in total phospholipid content but resulted in a selective loss of 1,2-diacyl-sn-glycero-3-phosphorylethanolamine (phosphatidyl ethanolamine, GPE). The quantity of GPE in denervated muscles was found to be significantly less than that it controls (p less than 0.01) within one day for short-stump preparations, as compared to three days for long-stump preparations. Also, direct comparison of short- and long-stump GPE values showed significant differences (p less than 0.01) at all times from the first to the fifth day following denervation, with no difference detected thereafter. These results imply that maintenance of skeletal muscle GPE involves a neurogenic influence which is independent of nerve-evoked muscle activity. This conclusion may help us understand neuromuscular diseases in which perturbation of phospholipid components has been implicated.