A method is described for the preparation of plasma membranes from human tonsil lymphocytes. The membrane preparation has been characterized by electron microscopy and by the use of 5'-nucleotidase as an enzymatic marker. Acrylamide gel electrophoresis in sodium dodecyl sulfate yields a reproducible pattern for the membrane proteins and glycoproteins. A minimum of 26 polypeptide bands were identified with the Coomassie blue stain. The glycoprotein material was distributed into at least five bands. Similarities and differences between the lymphocyte and red cell membrane are discussed.