The invention relates to a filter (1) for a vena cava made up of a head (2) and strands (5, 7, 9) formed or with shape memory forming a tail, attached to the head (2) and located on the same side relative to the head (2), the strands longitudinally constituting three levels of contact with the inner wall of a vena cava separated from one another and comprising three or four long strands (5) having different lengths of distal contact level, forming an elongate S, four to eight strands (7) of medium length having medium contact level, having at least three different lengths, and three or four short strands (9) having proximal contact level, the longitudinal separation under stress between the end of the long strands and that calculated on the medium length of the medium length strands being 15 to 30 mm.
