Human erythrocytes suspended in isotonic solutions were subjected to hemolysis by application of an electric field pulse to the cell suspension. The field strengths used were 12 and 16 kV/cm, respectively. The pulse duration was 40 .mu.s. The lysed cells showed resealing properties. The permeability change of the membrane generated by the field pulse and by the subsequent osmotic processes was large enough to facilitate the penetration and entrapment of ferritin and latex particles (diameter: 0.091 and 0.176 .mu.m, respectively) as revealed by EM. Correct identification of the latex particles in the electron-micrographs indicated that Loyter et al. who recently demonstrated the entrapment of latex spheres in erythrocytes prepared by osmotic hemolysis mistook electron-dense bodies probably consisting of denaturated protein for latex particles. Under conditions of osmotic hemolysis, carried out according to Bodemann and Passow, particles could only occasionally be detected within the membrane itself and never within the cell interior, suggesting that the electrical hemolysis method is much more effective in the generation of large holes in the membrane.