To describe trajectories of aggressive behaviors for adolescents living in rural areas, we compared the patterns, timing and sex differences in development of physical and social aggression using five waves of data collected from youth in school surveys administered over 2.5 years. The sample (N = 5,151) was 50.0% female, 52.1% Caucasian and 38.2% African-American. Multilevel growth curve models showed that physical and social aggression followed curvilinear trajectories from ages 11 to 18, with increases in each type of aggression followed by subsequent declines. Physical aggression peaked around age 15; social aggression peaked around age 14. Boys consistently perpetrated more physical aggression than girls, but the trajectories were parallel. There were no sex differences in the perpetration of social aggression. Given the characteristics of the developmental trajectories observed, interventions with both boys and girls targeting physically and socially aggressive behaviors are needed in early adolescence to slow the development of aggression.