Rolandic cortex was imaged with magnetic resonance (MR) in nine subjects while performing a motor activation task. Imaging was performed by a volumetric, T2-weighted pulse sequence in a conventional 1.5 Tesla scanner during both resting conditions and volitional toe flexion and extension of the dominant foot. Significant changes in MR signal intensity of 7.8 +/- 2.3% (mean +/- s.e.m.) were observed in the medial Rolandic cortex contralateral to the active foot. Changes were maximal in the vicinity of the central sulcus, but were also identified anteroposteriorly, across successive coronal planes. No significant changes were found in the ipsilateral Rolandic cortex or in other brain structures. Volumetric functional MRI strategies may provide an important non-invasive tool for assessment of cortical motor function.