The growth of a small arteriovenous angioma over a period of almost 18 years in a 20 year old patient has been proved by arteriography. This case is added to 29 cases previously published in the literature. The authors do not readily accept the theory of autochthonous growth, but prefer secondary or "pseudo-growth". In favour of this there are the following factors: 1. Not all arteriovenous angiomas observed over long periods show growth. 2. There are undoubted haemodynamic circulatory disturbances with turbulence, "wind-pocket effects", and abnormal shunts. 3. After complete removal of an angioma the cerebral circulation becomes normal and there is regression of the dilatation of the feeding and draining vessels.