Centrifugal SPLITT fractionation, a technique designed for the continuous high-resolution separation of colloids and low-density particles, is applied here to fresh human blood, producing six purified fractions consisting of proteins and lipoproteins, platelets, red blood cells, lymphocytes, monocytes, and neutrophils. Production of the six fractions requires five steps, each yielding two fractions. These five steps are carried out in sequence using a single apparatus, with conditions varying from step to step in accordance with theoretical guidelines in order to achieve the desired cut points. In the first step, a stream of diluted blood is separated into one fraction consisting of platelets and plasma and another containing blood cells. The throughput of diluted blood is 162 mL/h and that of whole blood is about 2 mL/h or similar to 10(10) cells/h; guidelines are given for significantly increasing throughput. The purity of the blood cell fractions ranged from 92 to 98%, and the viability fell in the range 97-99%.