Dicumarol anticoagulation poved very effective in the prevention of thromboembolic complications after aortic valve replacement with the Björk-Shiley tilting disc valve. We have, however, encountered six late deaths because of massive cerebral hemorrhage, which represent 3% of the patients who were maintained on dicumarol medication at that time. This unacceptable mortality prompted us to introduce two programmes, one without anticoagulation and another one with dipyridamole-acetylsalicylic acid. Furthermore, dicumarol was terminated in patients with haemorrhagic episodes, instable anticoagulation, pregnancy, and in those reguiring surgery. The results were disappointing, however, and the majority of the patients involved were therefore put on dicumarol medication. Eleven of the 64 consecutive patients taking dipyridamole - acetylsalicylic acid had thrombo-embolic episodes during a mean follow-up period of 9 months...