It was shown in Part III of this series, that purification by zone electrophoresis afforded a homogeneous callicrein (product L, 570U/mg.) from hog pancreas. The isoelectric point of this homogeneous callicrein was measured in order to elucidate its physical and chemical properties. The method of paper electrophoretic analysis, reported by Kunkel and Tiselius, which enables measurement of a micro-quantity, was used. Dextran, which is considered to be in uncharged state, was run with callicrein in order to correct the migration distance of callicrein. This result showed that the isoelectric point of homogeneous callicrein obtained from hog pancreas is at around pH 2.4. For staining of dextran, a 1% ethanolic solution of bromphenol blue is used and stained sample is washed by drops of ethanol.