A method is described for the isolation of nuclei from the leaves of higher plants. It is fairly rapid and up to 30 per cent of the total nuclei of the leaves of some plants may be recovered uncontaminated with other organelles and undamaged according to microscopical criteria, except for rupture of the nuclear membrane. The improvement of yields and the speed of isolation were achieved by a preliminary infiltration of the leaves with enzymes which attack the plant cell wall. In other respects the method resembles earlier procedures.