This chapter reviews rodent tests most commonly used to screen experimental manipulations (e.g., pharmacological, genetic mutation) on murine anxiety-like behavior, and highlight recent strategies for examining basic systems related to anxiety and stress (e.g., glyoxalase 1, corticotropin releasing factor, serotonin, and stathmin). The animal models described in this chapter (e.g., fear-potentiated startle, conditioned fear, and approach/avoidance conflict tests) have been instrumental to examine the physiological underpinnings of state anxiety and fear, develop anxiolytic compounds, and, more recently, to understand genetic and environmental influences on “trait” anxiety.