The aim of the present study was to investigate the effects of toluene on fetal development in well nourished and malnourished rats. Long-term behavioural consequences after in utero exposure were also studied. Toluene (1.2 g/kg s.c.) was administered daily to well nourished and to malnourished (food restricted to 50% of ad libitum intake) pregnant rats, during the second (8-15 days) or the third week of pregnancy (14-20 days). Offspring were evaluated for malformations, development of the skeleton, prenatal growth of the brain and liver, postnatal growth and long lasting behavioural effects. In utero exposure to toluene during the third week of pregnancy resulted in low body weight at birth, which persisted in the male offspring into adulthood. Malnutrition increased fetal susceptibility to the effects of toluene as indicated by evaluation of the development of the skeleton. Behavioral tests performed when the pups were 30 and 90 days old showed effects of in utero malnutrition (increased ambulation and worse performance in a shuttle box), but no behavioural effects related to toluene exposure were detected. These data indicate that in utero exposure to toluene can have long lasting effects on body growth and that maternal malnutrition increases the risk for toluene fetotoxicity.