Two familial cerebro-vascular diseases characterized by different cerebral arterial pathologies and presenting in non-hypertensive young and middle-aged adults are described. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by the deposition of smudged periodic acid-Schiff (PAS)-positive granules known as granular osmiophilic materials (GOM) in the media of small arteries and arterioles. The medial smooth muscle cells are completely lost, and intense adventitial fibrosis is present. Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), or Maeda syndrome, is characterized by intense arteriolosclerosis without GOM deposition. Fibrous intimal proliferation, hyaline degeneration of the media, thickening and splitting of the internal elastic lamina, and concentric narrowing of the lumen are characteristic features. In PAS preparation, small arteries are occasionally stained homogeneously due to exudative changes, but never exhibit granular appearance in CARASIL (Maeda syndrome). Each of the small arterial changes is intense in the cerebral medullary and leptomeningeal arteries, leading to multifocal, confluent, or diffuse ischemic changes in the cerebrum. The authors suggest that CARASIL be referred to as 'Maeda syndrome' or 'CARASIL (Maeda syndrome)' to avoid confusion with CADASIL.