Either phencyclidine hydrochloride (PCP) (5, 10, or 20 mg/kg) or saline was administered by subcutaneous injection to gravid CF-1 mice during either Mid (E6-15) or Late (E12-18) gestation. A nontreated control group (UTC) was left undisturbed during pregnancy. All treated and control litters were fostered at birth to untreated dams. Although postnatal challenge of PCP increased motor activity and ataxia in a dose-related manner, prenatal PCP had no effect on postnatal motor activity, ataxia or 3H-PCP binding. However, treatment period did have a significant effect on ataxia and 3H-PCP binding. In response to challenge doses of 5.0 and 7.5 mg/kg PCP, ataxia scores of the Late gestation offspring were significantly greater than the UTC offspring which in turn were significantly greater than the ataxia scores of the Mid gestation group. The results are discussed in relation to other animal and clinical reports of prenatal PCP exposure.