本研究の目的は,異年齢交流活動における幼児の社会的行動の発達について検討することであった。4 名の幼児(男児1 名,女児3 名)が3 歳から5 歳まで継続して観察された。その結果,3 歳時点では「世話する-される」関係,すなわち5 歳児は世話する人,3 歳児は世話される人であったが,4歳時点ではそれ以外の関係がみられるようになり,5 歳時点では社会的コンピテンスの高低に関わらず,「世話する」関係へ発達したことが明らかになった。その理由としては,いずれの群に対しても,5 歳児としての役割が与えられたことにあると考えられた。 The purpose of this study was to investigate the development of the social behavior of children in a multi-age program. One boy and three girls were observed from 3 years old to 5years old in a multi-age program. They consisted of the high group (two girls) and the low group (one boy and one girl) in the scale of social competence. The results were as follows: (1)In the 3 year-old class, there was a vertical relationship between the 5 year-olds and the 3 year-olds. The 5 year-old was the person who takes care, while the 3 year-old was the person who is taken care of. (2)In the 4 year-old class, behavior without the vertical relationship was observed in the case of the high-group children. On the other hand, the low group-children remained in the same relationship as in the 3 year- old class. (3)In the 5 year-olds class, the subjects of both groups took care similarly of the young children. One for reasons, this seemed to be that this role has given to them as the eldest children by the nursery teachers. Finally, it was suggested that a multi-age program was effective in the development of social behavior in the children.