A method for obtaining of the colloidal gold with particles 20 nm in diameter is described. The use of conjugate of colloidal gold-specific antibodies to the neutral DNAase is shown to determine the DNAase localization on ultrathin epontic sections of rat liver fixed by glutaraldehyde. The conditions of fixation, filling and immune reactions are described. The neutral DNAase has been found to localize mainly in heterochromatin.