The social structure of peer groups also was examined. Boys reported becoming angry more often than girls and were more likely to use direct means of aggression such as physical violence. Girls were more likely to express their aggression indirectly through circumventory behaviors that exploited social relations among peers. Gender differences in verbal aggression were less pronounced. Friendship groups were larger among boys and girls, with girls more likely to report pair relationships than boys. The correlation between self- and peer-ratings were higher for direct than for indirect aggression for both the total sample and for boys. Interviews indicate that girls felt their aggression to be of longer duration than did boys, who mentioned an usual duration of only a few minutes. Interviews also confirmed that girls were more likely than boys to use indirect aggression and that they viewed their peer relations as of greater emotional significance than did boys. Findings may help explain the generally lower correlation between self- and peer-ratings of aggression for girls than for boys (indirect aggression being less readily recognized by the subject of the aggression) and the low stability of aggressiveness in girls often found in developmental studies. 3 tables, 2 figures, and 19 references. (Author abstract modified)