Effects of the two oriental medicinal prescriptions, Jahyulyangeuntang (JH) and Yanghyuljangeunkeonbohwan (YH), on intestinal calcium absorption were examined in the human colon carcinoma tell line, Caco-2 cells. Intestinal calcium absorption was evaluated at the level of Ca uptake into the cells across the brush border membranes, as well as at the level of net Ca transport (implying the amount of intestinal Ca transported into the blood stream). When the Caco-2 cells were incubated for 4, 8, 16 and 24 days post seeding, the cells were differentiated continuously, and showed progressively increased activities of Ca uptake (1.13 $pm$ 0.04, 1.19 $pm$ 0.02, 1.94 $pm$ 0.03, and 2.40 $pm$ 0.12 nmole.mg protein$^{-1}$ .30 min$^{-1}$ , respectively). Pretreatment of confluent Caco-2 cells with 50 $mu extrm{g}$/ml of YH for 24 hours resulted in a 30% increase in Ca uptake (p < 0.07), while pretreatment of the cells with the same concentration of JH for 6 hours resulted in a 24% increase (p < 0.05) in Ca uptake, compared to the value for the control cells (2.34 $pm$ 0.10 nmole.mg protein$^{-1}$ .30 min$^{-1}$ ). When the cells were pretreated with varied concentrations (5-100 $mu extrm{g}$/ml) of the test samples for 6 hours, maximal increases in Ca uptake were observed in the cells pretreated with 100 $mu extrm{g}$/ml of YH (a 23% increase), and 50 $mu extrm{g}$/ml of JH (a 28% increase), respectively : however, no influence was seen on the net Ca transport activity. These results show that pretreatment with JH or YH, the two oriental medicinal prescriptions commonly used for improvement of bone metabolism, could possibly increase Ca accumulation inside the cells. but not the intestinal Ca net transport in vitro.