In order to study the biochemical mechanisms responsible for the membrane fatty acid deficiency in juvenile neuronal ceroid-lipofuscinosis, we have analyzed the reacylation pathway in isolated erythrocyte membranes in 5 patients. We studied membrane carnitine palmitoyl transferase, and developed a combined assay to study acyl-CoA synthetase and lysophospholipid acyl-CoA acyltransferase activities. There were no significant differences between control and patient membranes, suggesting that abnormalities in these 3 putative candidate enzymes are not responsible for the disease.