The correlation between boys' social cognitions and their aggressive behavior toward peers was examined as being actor driven, partner driven, or dyadic relationship driven. Eleven groups of 6 familiar boys each (N = 165 dyads) met for 5 consecutive days to participate in play sessions and social-cognitive interviews. With a variance partitioning procedure, boys' social-cognitive processes were found to vary reliably across their dyadic relationships. Furthermore, mixed models regression analyses indicated that hostile attributional biases toward a particular peer were related to directly observed reactive aggression toward that peer even after controlling for actor and partner effects, suggesting that these phenomena are dyadic or relationship oriented. On the other hand, the relation between outcome expectancies for aggression and the display of proactive aggression appeared to be more actor driven and partner driven that dyadic.