Poly(methyl methacrylate) (PMMA) chains were graft-copolymerized on a poly(tetrafluoroethylene) (PTFE) surface, and the tethered PMMA chains were spin-labeled to study the molecular motion of the PMMA chains by electron spin resonance (ESR). Two spectral components, a "fast" (isotropic) and a "slow" (anisotropic) component, with different rates of motion were observed in a certain temperature range. The isotropic and anisotropic components of the ESR spectra are identified with the fast and slow regions of polymer chain motion, respectively. Two transition temperatures, T-L and T-H, and the difference between T-L and T-H, Delta T, were estimated. The lower T-L is where the sharp N-14 isotropic triplet spectrum first appears as the sample is warmed, while the upper T-H is where the broad spectrum identified with the anisotropic pattern finally disappears. It was found that the transition temperatures and the Delta T of the tethered PMMA chains increased, had maximum values around ca. 3% grafting ratio, and decreased toward the transition temperatures and the Delta T of PMMA homopolymer chains with an increase in grafting ratio. The T-L for the sample with 1.2% grafting ratio is about 40 K lower than that for PMMA homopolymer, whereas the T-H for the grafting sample is 30 K higher than that for the homopolymer. These facts reflect a nide distribution of molecular structure of the tethered chains. The mobile chains protrude from the PTFE surface and have an extremely low segmental concentration of the PMMA molecules. On the other hand, the rigid chains take an entangled structure and are adsorbed on the PTFE surface.