SynopsisAn approximate analytic expression for the translational friction coefficient of a toroid modeled a s a continuous shell of frictional elements is derived using the Kirkwood approximation. The accuracy of this expression was determined by comparing the friction coefficients predicted by it to those predicted,by extrapolated shell-model calculations using the modified Oseen tensor. T o show that these calculatiops do indeed yield the correct friction coefficients, actual translational friction coefficients were determined by observing settling rates of macroscopic model rings or toroids in a high-viscosity silicone fluid. Our conclusion is that the approximate expression yields friction coefficients that are about 1.5-3%) low for finite rings. For thin rings, a comparison is also made with the exact result of Yamakawa and Yamaki [J. Chem. Phys. 57,1572Phys. 57, (1972 58,2049(1973l for the translational friction of plane polygonal rings. This comparison shows that the approximate expression yields results which are low by 2-3% unless t h e rings are extremely thin, in which case the error is larger. I n the limit of a n infinitely thin ring the approximate expression reduces to the Kirkwood result [ J . Polym. Sci. 12, 1 (1954)], which is low by 8.3%. We discuss hriefly how this work may he useful in determining the structure of DNA compacted by various solvent-electrolyte systems and polyamines.