Cytosine arabinoside (ara-C), an antiproliferative agent, was given subcutaneously to Sprague-Dawley rats on the 2-4th postnatal day in doses of 12.5 and 25 mg/kg/day. Body weight and viability were found to be dose-dependently inhibited. The appearance of audio-startle response was delayed in the group on the high dose and up to 21 days of age, the ambulatory behavior resembled that seen in geriatric rats. The free-fall righting reflex failed to appear in the treated groups. The open field test revealed that only the treated females were hypoactive. The treated group showed a poor neuro-muscular ability in the rotarod performance and impairment of acquiring conditioned and unconditioned avoidance response in pole climbing. Histopathological and biochemical studies revealed a hypoplasia of the cerebellum. These findings are suggestive of behavioral dysfunction caused by ara-C-induced cerebellar disorders.