To specify different modes of individual children's social integration, this study examined qualitative and quantitative aspects characterizing distinct types of peer relationships. Subjects were 255 children in grades 2 through 5 of an inner-city primary school in Berlin, Germany. Subjects were individually interviewed at school about their friends, and were asked to nominate all children with whom they had contact outside school. A subsample of 116 children and their parents were additionally interviewed at home about further characteristics of their friendships, their concept of friendship, the quality of the parent-child relationship, and other characteristics of family life. Three descriptive scales (assistance, fun, and absence of quarreling) were developed and confirmed by factor analysis to be different dimensions of relationship descriptions. Analysis revealed that children described same-sex relationships as more intense than opposite-sex relationships. Having opposite-sex relationships and getting assistance and fun in opposite-sex relationships was positively related to social and cognitive development. The same result was not found for same-sex relationships. Relationships with classmates were of higher importance for children's feeling of acceptance than relationships with non-classmates. Finally, analysis showed that reciprocal relationships were more intense and provided more assistance and fun than non-reciprocal relationships. (MM)