Analyzed defensive behaviors in a seminatural setting through videorecordings of groups of 4 male and 4 female rats. Before cat exposure dominant males showed more offensive behavior, eating, drinking, and use of the open area than subordinates. Presentation of a cat in the open area produced changes in four subpatterns of defense over a 24-hr period: withdrawal; immobility and movement constraint; risk assessment; and suppression of nondefensive behaviors. All Ss showed pronounced and consistent changes in each of these patterns, but dominant males alone showed increased risk assessment-related corner runs. These results provide an extensive description of rat defensive behaviors in a seminatural and relatively unstructured situation and suggest that the anxiety process is initially associated with withdrawal and movement arrest, giving way to a crucial and long-lasting risk-assessment stage that provides information leading to either further defensiveness or a return to nondefensive behaviors. This analysis suggests new models for the study of anxiety.