Grasping both the extent and the actual situation of psychosomatic disorders, neurotic habits and developmental disorders of infancy and childhood is vital for their prevention and for taking appropriate measures to deal with the current situation. The purpose of this study is to explore the current situation of infant mental health in Japanese day-care centres. The investigation regions for this study were Okinawa prefecture and Aomori prefecture in Japan. Our investigation method was a mailed survey, which was answered by the director or a teacher of the day-care centre. The response rates were 40.9% (Okinawa) and 41.2% (Aomori). This included the answered surveys from 78 day-care centres (6250 children) in Okinawa and 134 day-care centres (9613 children) in Aomori. We found that the approximate prevalences of mutism in infants and children in the above-mentioned day-care centres were 0.34% (Okinawa) and 0.33% (Aomori). In the same way, the rates of tic disorder were 0.51% (Okinawa) and 0.54% (Aomori), and the rates of elimination disorder were 0.30% (Okinawa) and 0.28% (Aomori). These rates did not show any significant difference. When we compared the rates with those obtained from conventional studies, only slight differences were observed. (Contains 2 tables and 1 figure.)