Dielectric measurements were carried out on undiluted poly(isopropyl glycidyl ether) (PiPGE), poly(n-butyl glycidyl ether) (PnBGE), and poly(tert-butyl glycidyl ether) (PtBGE) which have dipoles aligned parallel (type A) and perpendicular (type B) to the chain contour and the dipoles residing on the flexible side group (type C). These polyethers exhibited three dielectric relaxations designated as alpha(n), alpha(s), and beta. The alpha(n) relaxation is due to the normal mode relaxation. The primary alpha(s) relaxation is assigned to local segmental motions coupled with rotation of the side group. The beta relaxation can be assigned to both twisting motions of the main chain and libration of the side groups of a small amplitude. Independent full rotation of the side groups was not observed below T-g. The relaxation strengths and dipole moments associated with the alpha(n), alpha(s), and beta processes have been estimated. In PiPGE and PtBGE, the temperature dependence of the loss maximum frequency f(ms) for the alpha(s) relaxation was much. steeper than that f(mn) for the normal mode, and log(f(ms)/f(mn)) increased with temperature. On the other hand, log(f(ms)/f(mn)) for PnBGE was almost independent of temperature.