We have recently reported that thiamine deficient (TD) mice show an impairment of learning and memory on the 20th day after start of TD feeding. Interestingly, it has been reported that the kampo medicine, "kami-untan-to" (KUT) may be useful as a potential therapeutic agent in diseases associated with cholinergic deficit such as Alzheimer's disease. In the present study, we investigated the effects of KUT on the impairment of memory-related behavior concomitant with psychoneuronal symptoms after TD feeding in mice. Oral administration of KUT had no effect on the food intake, body weight or locomotor activity in TD mice, but the mortality rate in the KUT-treated TD group was significantly lower compared with that in the non-treated TD group. Daily administration of KUT from the 1st day of TD feeding protected against the impairment of memory-related behavior induced by TD. The intensity of the choline acetyltransferase fluorescence decreased in the field of CA1 and dentate gyrus in the hippocampus in TD mice compared with pair-fed mice as the control group, and KUT treatment inhibited this decrease. These results suggest that the effect of KUT on the impairment of memory-related behavior induced by TD feeding may be closely related to the activation of cholinergic neurons in the hippocampus.