A procedure for venous and arterial catheterization is described which allows the quantitative 2-[14C]deoxyglucose method to be applied to freely moving animals for behavioral and pharmacological studies. The catheterization method is rapid, minimally invasive, and requires no complicated equipment. Physiological conditions and rates of cerebral glucose utilization in freely moving rats and in restrained rats have been compared. The results demonstrate that local cerebral glucose utilization can readily be measured in freely moving animals engaged in behavioral experiments.