Abstract: The filter is particularly for implantation in the interior vena cava by sliding through a small sized catheter of type 7F, so as to arrest the migration of all thrombi of dangerous size. The filter comprises a flexible wire having been subjected to a primitive predeformation into first and second substantially flat superposed loops. The loops are substantially symmetrical respectively with regard to two axes which are substantially orthogonal and convergent at a center of the filter. These loops can be elliptic and inscribed in a square, thus providing four contact points with the venous wall, which are in two-to-two symmetry with regard to the center on the longitudinal axis of the vein, which gives the filter high stability in the vein.