A prospective series of 60 consecutive patients with lacunar cerebral infarcts (LI), studied using nuclear magnetic resonance (MR) and brain computerized tomography (CT), is presented. A significantly greater number of positive results (p less than 0.001) was observed in the MR (78%) in comparison with the CT scan (30%). In pure motor hemiparesis, the number of positive results obtained with MR was maximal (85%) and greater than with CT scan (35%; p less than 0.001). In pure sensory stroke, the positivity was 40% in MR and 20% in CT. In pontine and capsular topography, MR showed a greater sensitivity than CT scan (p less than 0.001). A significantly (p less than 0.001 greater number of silent infarcts were detected by MR (42%) than by CT scan (18.5%). Nowadays, MR is the complementary examination of choice in the topographic diagnosis of LI and should be carried out whenever possible in all patients presenting with this pathology.