What is the connection between identity and conflict behavior? This article begins by exploring some of the theoretical currents in this area, notably social identity theory, Erikson's work on identity development, Burton's ontological needs, and image theory. The theories differ somewhat in their expectations of the effect of identity development. Two studies were conducted to investigate these differences. The first, a priming experiment, partitioned identity and its effects. The second, a group-based simulation study, measured actual development of ingroup identity and assessed its effect on conflict behavior. Results from the first study show that identity does affect conflict behavior, but only as it is mediated by levels of insecurity. Increased feelings of security correspond to more cooperative behavior. Positive and negative images of the opponent, on the other hand, did not influence conflict behavior. In the second study, higher levels of ingroup identity resulted in more conflictual behavior. As with the first study, image of the other was not significantly related to conflict behavior.