In a series of 230 observations of Crohn's disease, the authors describe 4 cases of arterial thrombosis; two of them involving cerebral arteries. These complications occurred in young women without any notable risk factor for atheroma. All patients had highly active Crohn's disease when arterial thrombosis occurred: two of them had several episodes of thrombosis and three, extraintestinal manifestations. As the arterial thromboses are often severe, rarely foreseeable and the venous thromboses frequent, the point is whether to use anticoagulants. When Crohn's disease is highly active, but only if there are no hemorrhagic lesions, anticoagulants at prophylactic doses may be recommended. How to define more exactly a high risk thromboses population deserves further investigation.