Abstract: Alkaline phosphatase isoenzymes with a specific activity of >40 fold and PAGE pure was isolated from the liver,kidney,bone and intestine of the newborn calf (First,each tissue homogentes was extracted in buffer butanol.Then,the aqueous phase was separated by filtration on Sephadex G-100,DEAE-cellulose column chromatography).The pure product was studied with respect to its enzymetic activity,electrophoretic mobilities (Rf value),heat inhibition,urea inhibition,organ-specific inhibitor treatment,to establish the identities of each isoenzyme.The results demonstrated the following:1.Isoenzymes Rf value:liver isoenzyme>bone isoenzyme>small intestine isoenzyme.2.Only the bone enzyme was completely inactivated when heated at 56℃ 10 min.Intestial isoenzyme was heat-stable.3.Urea was a strict inhibitor of bone isoenzyme and intestial isoenzyme was urea-stable.