This exploratory study investigated Mainland Chinese children's social networks and peer group affiliations with a particular emphasis on their aggressive behaviour. The participants were 294 elementary school students in Tianjin, P. R. China (mean age 11.5 years; 161 boys). Social network analysis identified relatively large and gender-specific peer groups. Although different measures were used, the pattern of homophily characteristic of Western aggressive children was partially supported. This finding may be due to the large size of the peer groups. The results showed that some aggressive children formed friendships with nonaggressive children. Moreover, for the aggressive children who were group members, the number of within-group friendships moderated the relation between aggression and overall peer preference. In addition, despite the moderating effect of within-group friendship, the relation between aggression and peer preference remained significantly negative even at the highest levels of friendship. Aggressive children who were isolated from all peer groups had higher hyperactivity ratings and were less liked by peers than were aggressive children who were group members. These findings illustrate how culture may be an influence on patterns of peer group affiliation. (Contains 3 tables and 1 figure.)