Physical and mental conditions of morning (M) and evening (E) type children were investigated while in class. Out of 111 sixth-grade children in an elementary school, 19 and 9 were classified as M-type and E-type respectively, based on the criterion of Horne and Ostberg. The results were as follows : 1. Children who felt sleepy, tired and not concentrative on learning in class were found more frequently in E-type than in M-type. 2. Children who had short sleep at night or who did not eat breakfast were also sleepy, tired and not concentrative in class. 3. E-type children tend to be short sleepers with no breakfast. These results suggest that E-type children are not in satisfactory condition for learning in school.