First‐order excluded‐volume effects on the intrinsic viscosity and translational friction coefficient of nondraining flexible ring polymers were calculated on the basis of the Kirkwood–Riseman formalism of polymer hydrodynamics. The cube of the viscosity expansion factor αη,r was found to be represented by α 3η,italicr = 1 + 1.18z + …, where z is the usual excluded‐volume parameter. Combination of this result with the corresponding calculation by Fujita et al., for nondraining linear polymers, yielded α 3η,italicr/α 3η,italicl = 1 – 0.11z + … (αη,l denotes the viscosity expansion factor for linear chains). The negative coefficient of the z term contradicts the conclusion by Tanaka and Yamakawa who used the Zimm–Hearst theory of polymer dynamics. The friction expansion factor αf,r, for ring polymers, was obtained in powers of z as αf,r/αf,l = 1 + 0.773z + …. The earlier evaluation of αf,r by Fukatsu and Kurata was in error. The ratio αf,r/αf,l (αf,l is the friction expansion factor for linear chains) was given by 1 ± 0.182z ± … when the corresponding result on αf,l was used. This expansion compares well with Casassa's result αs,r/αs,l = 1 ± 0.147z + … for the ratio of the radius expansion factors of ring and linear chains.