The distribution and some properties of alkaline phosphatase (ALP) were investigated in the midgut of the earthworm, Eisenia andrei. The ALP activity appeared to be highly polarized toward the luminal side of epithelium, with minor ALP activity in chloragogue tissue. The epithelial and chloragogeneous tissues contained approximately 85 and 15% of total intestinal ALP activity, respectively. The optimal temperature was approximately 37$^{circ}C$ and isoelectricpoint was estimated to be 4. The treatment of neuraminidase and PtdIns-PLC failed to change the migration rate of ALPs. Also, these ALPs appeared to have a wide range of substrate specificity. The relationship between the properties and physiological significances of the midgut ALPs in Eisenia andrei was discussed.