Evoked potentials (EPs) and nerve conduction velocities (NCV) were evaluated in 8 affected and 10 asymptomatic members of a new Italian family with an adult-onset autosomal dominant leukodystrophy of uncertain nosography. NCV studies did not show anomalies. Various EPs abnormalities were found in all the symptomatic patients (increase of interpeak latency and/or loss of cortical responses), according with a myelin disorder. Among the asymptomatic subjects 3/10 (30%) showed similar anomalies at auditory brainstem EPs (increase of I-III/I-V/III-V interval). Two of these patients had normal brain MRI. This datum require further confirms (very low penetrance of the disease?), but it remarks the importance of a functional study of SNC in order to obtain elements not usually given from clinical and neuroradiological study.