The effects of a continuous infusion of the calcium antagonist nimodipine (1 microgram kg-1 min-1) on local CBF (LCBF) and local cerebral glucose utilisation (LCGU) were studied, using the quantitative autoradiographic [14C]iodoantipyrine and [14C]2-deoxyglucose techniques in 34 anatomically discrete regions of the brain in lightly restrained, conscious rats. The infusion of nimodipine at this concentration produced only a small (8%) reduction in the MABP. The administration of nimodipine did not alter the rate of glucose utilisation in any of the regions examined. By contrast, in 24 regions, CBF was increased significantly by 39-84% from control levels (for example, cerebral cortices, hippocampus, hypothalamus, and most thalamic nuclei). In vehicle-treated animals, there was an excellent correlation (p less than 0.01) between the local levels of CBF and glucose utilisation, with the ratio of flow to glucose use being approximately 1.5 ml mumol-1 in each brain region. During nimodipine treatment, there was a similarly excellent correlation (p less than 0.01) between LCBF and LCGU, but the median ratio between local flow and glucose use increased to 2.5 ml mumol-1.