Two studies were conducted to examine age and sex differences in friends' activities and relations of participation in these activities to perceived friendship quality. In Study 1, 52 fourth and eighth graders were asked open-ended questions about activities they do with their best friends. In Study 2, 105 fourth and eighth graders reported both on perceived friendship quality and frequency of participation in 40 activities mentioned in Study 1. Eighth graders participated in more school, maintenance, media, and socializing activities with friends than fourth graders did. Boys participated in more sports and media activities with friends than girls did. Students who did more socializing, school, and maintenance activities with friends perceived more positive features in their friendships. These results suggest that engaging in some but not all types of activities with friends may enhance the development of high-quality friendships. (Contains 3 tables and 2 figures.)