Long-term treatment with the anticonvulsant valproate (VPA) leads to well-documented weight gain and obesity in humans. In an attempt to develop an animal model of this condition, adult rats were given VPA 20 g/kg (high-dose) or 2 g/kg (low-dose) in their daily feeding or orally 120 mg/kg body weight/day in two divided doses, and food intake and body weight were assessed. Valproate resulted in lower body weights in all protocols. Food intake was lower (p<0.001) for rats receiving high-dose VPA than for controls. Feed efficiency (change in weight divided by cumulative food intake for that period) was lower than that of controls for both high (p<0.0001) and low doses (NS). Metabolic rate and physical activity were not different between control and VPA animals, although decreased food intake would be expected to decrease metabolic rate. Valproate failed to produce obesity in rats in any treatment period. For reasons that are unclear, rats do not appear to be suitable as a model to study this adverse side effect of VPA in humans with epilepsy.