Consumption of arsenic-contaminated drinking water is associated with numerous cancers and dermal and vascular diseases. Arsenic is also a potent nervous system toxicant and epidemiological studies indicate that intellectual functions in children are compromised following early developmental exposure. This study was designed to examine the effects of arsenic on a broad range of age-specific behaviors including basic sensory-motor responses in neonates, locomotor activity and grip strength in juveniles, and operant measures of learning and attention in adults. Pregnant C57BL6/J mice consumed drinking water containing 0, 8, 25, or 80 ppm sodium arsenite from the fourth day of gestation until birth. Arsenic produced a range of behavioral impairments in male and female offspring at each of the test ages. The most striking effects of arsenic were on the development of gait and other motor responses including acoustic startle, righting reflexes, and forelimb grip. These results suggest that developmental arsenic exposure can produce other behavioral impairments in children in addition to cognitive impairment.