A small battery of tests (static and air-righting reflexes, eye opening and a narrowing bridge test) was used to investigate the behavioural teratogenic potential of prenatal oral exposure (day 7-19 of gestation) of up to 100 mg phenytoin/kg/day to female rats. No treatment-related effects upon mother or offspring were detected. In order to validate our narrowing bridge test, neonatal old rats were tested over 4 weeks following early postnatal exposure to acrylamide (5 X 50 mg/kg/day i.p.). These animals showed a severe transient deficit compared with saline-treated controls. Despite the absence of an effect using phenytoin, the narrowing bridge test is considered worthy of further validation.