Expression patterns of sugars on the mucosal surface of the uterus in pregnant mice were investigated by using 21 kinds of lectins. In the uterine mucosa, the GlcNAc group tended to express a positive reaction before pregnant day 10, but the glucose/mannose group generally expressed a positive reaction after pregnant day 10. On the other hand, the fucose group expressed a negative reaction during all periods in pregnancy. These findings were almost the same on both the mesometrial side and anti-mesometrial side of the uterus. These differences of sugar expression probably reflect the functional change of the mucosa during pregnancy and the alteration of sugar expression may give a chance for pathogens to infect in the uterus with limited periods.