A patient is described presenting with an acute lower gastrointestinal haemorrhage as a result of extensive colonic varices. Further investigation revealed that there were no oesophageal varices or splenomegaly. Liver biopsy showed grade II fatty change only, with no other specific or significant pathological features. Transhepatic portography showed a raised portal pressure (20 mm/Hg) but the portal system was patent throughout. There was an abnormal leash of vessels in the caecum thought to represent a variceal plexus. This patient was diagnosed as having idiopathic colonic varices. This case is discussed together with nine other reports of idiopathic colonic varices from the published literature. Four of these reports describe idiopathic colonic varices in more than one member of the same family. Possible modes of inheritance, aetiology of variceal change, natural history, and prognosis are discussed.