Defensive behaviors of lower mammals constitute a significant model for understanding human emotional disorders. They generally occur in response to a number of threatening stimuli, including predators, attacking conspecifics, and dangerous objects or situations. Such behaviors can readily be studied in wild rats, wild mice, or in several laboratory mice, which show a complete defensive repertoire in response to danger. Here we describe the mouse defense test battery (MDTB), which measures flight, freezing, defensive threat and attack, and risk assessment in response to an unconditioned predator stimulus, and postthreat (conditioned) defensiveness to the test context. The MDTB represents a significant improvement over other animal models for evaluating drugs active against emotional disorders since it is capable of responding to and differentiating anxiolytic drugs of different classes through specific profiles of effect on different measures.