A population of small unilamellar liposomes loaded with horseradish peroxidase, an electron dense marker, was prepared by passing the lipid-protein-detergent micelles through Sephadex G-50. By electron microscopy it was shown that these artificial lipid vesicles were incorporated into the cytoplasm of isolated pure cholinergic nerve endings from the electric organ of Torpedo marmorata. This liposome carrier system may be useful in manipulating the internal parameters involved in presynaptic processes in the electric organ.