Immunostaining method for the sensitive detection of isoferritins separated by isoelectric focusing on cellulose acetate membrane is described in this paper. Methanol was used in order to fix proteins to the membrane. Membrane was shaked in methanol immediately after isoelectric focusing and then incubated in phosphate buffered saline containing a sufficiency of antibody and 2% skim milk. Blocking, a step for filling in the blank of membrane was not necessary. Fine isoferritin profile with clear background was obtained using this procedure. The sensitivity of immunostaining was slightly higher than that of gold staining in which proteins were fixed with sulfosalicylic acid and/or trichloroacetic acid. When 250ng of liver ferritin was applied on the membrane, minor acidic isoferritin bands also were observed distinctly.