Developmental tests are used to characterize early markers of behavior for investigation of the neurobiology of these behaviors, and to assess the impact of early prenatal or postnatal insult. These perturbations may include pharmacological, environmental, and genetic manipulations. At birth the rat is capable of some specific activities, but its movements are uncoordinated and seemingly random, its tactile sensitivity is not fully developed, and its ear canals and eyes remain closed until several days after birth. Postnatal development consists mainly of the continuation of processes begun earlier. This unit presents protocols for the most commonly used animal tests of developmental reflexology, including negative geotaxis, cliff avoidance, placing responses, tactile and acoustic startle responses, surface and air righting reflexes, crossed extensor reflex, rooting reflex, grasp reflex, bar holding, and horizontal and vertical screen tests.