This technical report describes development work done on zonal centrifuge systems at the Oak Ridge National Laboratory and the Oak Ridge Gaseous Diffusion Plant during the period July 1 to December 31, 1962 under the Joint National Institute for Health-Atomic Energy Commission Zonal Centrifuge Development Program. A basic purpose of this project is to develop new methods for isolating virus particles associated with cancerous cells and tissues. Three classes of rotor systems capable of separating particles ranging in size from whole animal or plant cells to protein or nucleic acid molecules on the basis of either sedimentation rate or density alone have been developed. Experiments with phage particles indicate the feasibility of large-scale virus isolation by continuous-flow centrifugation, followed by isopycnic banding in cesium chloride and velocity sedimentation in sucrose - all steps being carried out sequentially in the same rotor. Zonal rotors using the reorienting gradient principle for molecular separations have been tested to 141,000 rpm (formula). Previous work on zonal centrifugation and future plans for this program are discussed.