The physical aging of a poly(methyl methacrylate) (PMMA) copolymer having a small amount of ethyl methacrylate was investigated below its glass transition temperature (T-g) using dynamic viscoelastic measurements. The results were compared with those from homo-PMMAs to investigate how the comonomer in the copolymer affects the physical aging of the glass. Annealing temperatures were classified into two categories by the glass transition temperature of a poly(ethyl methacrylate) (T-gPEMA; ca. 65 degreesC). The relaxation rate of the copolymer into two categories by the glass transition temperature of a poly(ethyl methacrylate) was faster than those of the homo-PMMAs when the samples were aged below T-gPEMA, but the rates were equal when aged at above T-gPEMA. The experimental results are discussed in terms of the segmental motion.