Apart from special types encountered in neonates and during pregnancy, spontaneous sub-capsular haematoma (SCH) of the liver is a rare condition which is usually not recognized before operation. The diagnostic value of arteriography is emphasized by this case of SCH in a 29 year old man which presented spontaneously with the appearance of a large mass in the right hypochondrium with fever and pain. Angiographic changes identical to those seen with a traumatic SCH were found and, in this case, were accompanied by a local reversal in intra-hepatic portal flow related to a tumoural Budd-Chiari phenomenon (compression of the hepatic veins by the haematoma). Despite histological study of the liver, no tumoural, vascular, infective or parasitic aetiology could be found to explain this apparently idiopathic spontaneous SCH.