Brain-stem auditory evoked responses (BAERs) and somatosensory evoked responses (SERs) were studied in three patients and seven female relatives in three families with adrenoleukodystrophy (ALD). All patients with ALD had abnormal BAERs and SERs, reflecting the central demyelination occurring in ALD. Four of the seven female family members had abnormalities of SERs with or without abnormalities of BAERs, similar to those seen in the patients. We suggest that these abnormalities demonstrate the morphological effects of the ALD gene in the CNS and reflect the physiological alteration in the heterozygous females in families with ALD.