Multislice spin echo (SE) pulsed-field gradient phase-contrast (PFG-PC) magnetic resonance imaging (MRI) velocimetry, has been used to determine the complex three-dimensional (3-D) recirculatory flow pattern of a simple, single-phase blood analogue fluid (glycerol-water solution 70-30 vol%) in a commercially available blood filter (PALL AL8 arterial line blood filter), whose inlet and outlet ports are about 0.95 cm in diameter. The maximum shear stress measured in the fluid is 10 Pa, which is significantly lower than the value for the onset of red blood cell hemolysis. The flow field is in agreement with computational flow modeling (Fluent 4.3) and is reminiscent of the hydrocyclone flow in industrial separation devices. The development of this flow pattern is demonstrated for three different volume flow rates (1, 2, and 3 L/min). (c) 2005 American Institute of Chemical Engineers.