A study of elderly patients (fourteen men, sixteen women) who were admitted to hospital with acute illness and extreme self-neglect revealed common features which might be called Diogenes syndrome. All had dirty, untidy homes and a filthy personal appearance about which they showed no shame. Hoarding of rubbish (syllogomania) was sometimes seen. All except two lived alone, but poverty and poor housing standards were not a serious problem. All were known to the social-services departments and a third had persistently refused offers of help. An acute presentation with falls or collapse was common, and several physical diagnoses could be made. Multiple deficiency states were found--including iron, folate, vitamin B12, vitamin C, calcium and vitamin D, serum proteins and albumin, water, and potassium. The mortality, especially for women, was high (46%); most of the survivors responded well and were discharged. Half showed no evidence of psychiatric disorder and possessed higher than average intelligence. Many had led successful professional and business lives, with good family backgrounds and upbringing. Personality characteristics showed them to tend to be aloff, suspicious, emotionally labile, aggressive, group-dependent, and reality-distorting individuals. It is suggested that this syndrome may be a reaction late in life to stress in a certain type of personality.