This study examined associations between popularity trajectories and changes in proactive and reactive aggression in middle adolescence. The sample included 1374 adolescents from five cohorts who were followed from grade 7 to grade 9 (49% males, Mage= 12.67 years, SD = .67). Popularity trajectories were identified based on initial status and changes in status over time, and linear mixed effects models tested group differences on changes in aggression. The results partially confirmed our expectation that changes in popularity were associated with specific developmental patterns of proactive and reactive aggression and also varied as a function of status already achieved. Specifically, adolescents in groups characterized by gains in status increased in proactive aggression, and those in groups characterized by loses in status decreased in proactive aggression. A more nuanced pattern of group differences emerged for reactive aggression. Changes in reactive aggression were only found for adolescents groups characterized by changes in unpopular status. Taken together, these findings suggest proactive aggression has universal benefits for status in middle adolescence, whereas reactive aggression has differential costs. Implications and directions for future research were discussed.All information about the content of the files is described in 'read me.pdf'. This file also contains information about the recruitment, participants and data collection. Data and the sytax for the analyses as presented in the paper are also stored.