The present invention relates to a non-evertable blood filter that divides the transverse cross sectional area of a venous vessel into three annular regions or zones. The inner zone, the region immediately surrounding the longitudinal axis of the vessel, is maintained in a relatively open state with only minimal interference from the members making up the filter device so that blood flow can be maintained at a relatively normal rate. Concentrically surrounding the inner zone is the intermediate zone, to which captured emboli are directed out of the bloodstream passing primarily through the inner zone. Finally, concentrically surrounding the intermediate zone is the outer zone adjacent to the vessel wall. This is also intended to be kept free of emboli, so that emboli in the bloodstream immediately adjacent the vessel wall are directed away from the wall by the filter design and into the intermediate zone, thereby avoiding the accumulation of emboli adjacent the vessel wall that might otherwise result in stenosis. The blood filter is intended primarily for use as an inferior vena cava filter, although it can be made in a range of sizes allowing its use in blood vessels and particularly venous vessels of differing diameters. The filter is preferably removable.
