Spherical vesicles of sarcolemma (media diameter, 78 microns) were prepared from frog skeletal muscle by prolonged exposure to enzymes (collagenase, then protease) and to isotonic KCl solutions, which promote swelling of muscle fibres. Patch clamp recording was used to measure unitary K and Na currents from this preparation. Na and K channels had conductances around 15 pS and their kinetic properties appeared unaltered by vesicle formation.