Embolization plays a major role in the management of arteriovenous malformations and fistulae on one hand, and of venous malformations and cystic lymphangiomas on the other hand. The treatment of arteriovenous fistulae today resorts to a primarily endovascular technique including the insertion under controlled flow of a releasable balloon or of a metallic coil positioned in the area of the fistula. Of course, this is possible only if there is a gap between the arterial and venous pathways. When the vessels are in direct contact, surgery must be preferred. In cases of arteriovenous malformations, embolization currently plays a great role; either it is performed with particles in the immediate preoperative period, two or three days before surgery, or as a definitive curative treatment with a polymerizing substance applied in situ. The use of flexible microcatheters allows penetrating into most of these vascular malformations and scattering polymerizing material all over the shunting areas. This is possible for superficial malformations, as is now performed, for instance, for brain AVMs. This embolization obviously can be contemplated only after a decision to treat these malformations has been made, knowing that they may be silent or acquire an uncontrollable evolution potential. This therefore is a collegial decision. As far as venous hemangiomas and cystic lymphangiomas are concerned, the greatest basic therapeutic means today is direct puncture and the in situ injection of a fibrosing substance under angiographic monitoring: the use of Ethibloc or, failing this, of absolute alcohol, has dramatically transformed the prognosis of these malformations, for which the surgical difficulties are well known (easy rupture, blood that often fails to coagulate, life-long progressive evolution).(ABSTRACT TRUNCATED AT 250 WORDS)