In our medical and welfare facilities, many patients with senile dementia require aid in taking a bath. In most institutions, patients usually take a bath in the daytime within the working hours of the staff. However, most of these patients used to take a bath in the evening or at night at their homes. Some patients even fall asleep after daylight bathing. Thus, we studied the stabilizing effects of night-time spa bathing on symptoms associated with dementia. Ten patients (two male and eight females, aged 75-88) in special nursing institution for the aged, were enrolled in this study. They were all assessed as +4 on the Karasawa's clinical criteria for grading dementia. For 9 weeks, night-time spa bathing was performed at 18:00-19:00 twice a week. Except for the night-time spa bathing period, the bathing hour was 14:00-15:00 as usual. The observations of symptoms including restlessness, wandering and aggression were carried out ten times daily along with those on sleeping condition five times daily, to compare symptoms and conditions during 2 weeks of baseline daytime bathing periods, 9 weeks of night-time bathing periods and 2 weeks of daytime bathing periods, totaling 13 weeks. The results showed that sleeping conditions were ameliorated in more than 60-90% of the subjects. Their sleeping conditions began to improve 2 weeks after the start of night-time spa bathing with a remarkably improvement 4-6 weeks after the start. Restlessness was recognized in six subjects, wandering in eight and aggression in four at baseline, and 75-100% of the subjects with such symptoms improved markedly.