By cellulose acetate or acrylamide gel electrophoresis it is possible to separate these alkaline phosphatase isoenzymes from serum: [anode] fast liver, slow liver, placenta/Regan, bone, intestine, bile [cathode]. Heat or chemical inhibition can confirm the differentiation.Normal adult serum always contains slow-liver isoenzyme, and sometimes bone isoenzyme: the latter is always present in serum of children. In hepatobiliary disease slow-liver isoenzyme was always increased: intestinal isoenzyme appeared in many cases of cirrhosis (of blood groups B and 0) but fast-liver and bile isoenzymes were occasionally seen in miscellaneous cases. The findings in other diseases included Regan isoenzyme in six out of 45 cases of malignant disease.