Abstract: A process for separating plasma or serum from mammalian whole blood includes the steps of applying a sample of blood through a hydrophobically faced sample receiving hole positioned in a first upper layer of hydrophobic material to a first layer of fibrous hydrophilic material which has been impregnated with a blood agglutinating agent so that it acts to retain red blood cells but not plasma or serum and layer is sealed at its upper edges to the first layer of hydrophobic material and allowing the liquid portion of the sample to flow downwardly through the first layer of fibrous hydrophilic material into a second layer comprised of a different fibrous hydrophilic material which second layer is sealed at its lower edges to a second layer of hydrophobic material whereby it acts to retain the plasma or serum.