Four cases (belonging to two different families) of Wolfram's syndrome (WS), a rare congenital disease characterized in its complete form by insulin-dependent diabetes mellitus, optic atrophy, diabetes insipidus, deafness, and dilation of the urinary tracts are presented, and a review of the literature is included. Three of four patients are characterized by HLA-DR2 haplotype, which is rare in IDDM. The neurodegenerative nature of some symptoms and the possible pathogenesis of diabetes mellitus connected with it are discussed.