Alkaline phosphatase (ALP) hydrolyzes a variety of monophosphate esters into inorganic phosphoric acid. Intestinal ALP seems to play an important role in active metabolism by hydrolyzing phosphocompounds to supply free inorganic phosphate, but little is known about the physiological function of intestinal ALP. This study investigates the effects of powdered green tea added to the control diet on the intestinal ALP activity in rats. Sprague-Dawley female rats (6 weeks old) were assigned to a control group and powdered green tea group. Rat intestinal segments from the duodenum, jejunum and ileum were obtained two months after starting the respective diets, and used for an enzyme assay. The intestinal ALP activities in both the duodenum and jejunum from the rats in the powdered green tea group were significantly lower than those from the control rats. These findings suggest that powdered green tea is one of the factors that affects intestinal ALP activity.