Lacunar lesions are small infarctions in the territory of small penetrating arteries of the brain. Because of their small size these lesions can only in part be detected by CT. Clinical symptoms do not always correspond with the lesions visible in the CT. We studied the somatosensory evoked potentials (SEP), the visual evoked potentials (VEP) and the electrically elicited blink reflex in 50 patients with lacunes to determine if there are any other lesions which are not detectable by clinical examination or CT alone. While VEP and the blink reflex showed pathological results in only a few of these patients the SEP were pathological in about 75%. The multiplicity of the lesions may be documented by means of these investigations.