100 MHz C-13 NMR spectra of methyl methacrylate/tert-butyl acrylate copolymer, PMMA/tBA, reveal configurational effects of both comonomers. The microstructure of the macromolecular chain has been determined utilizing carbonyl and beta-CH2 carbon signals and the spectral assignments were performed in terms of the configurational-compositional sequences. To determine the line positions of individual sequences, the incremental method of the chemical shift calculation has been applied. Based on these data, the analyzed signals were simulated yielding fairly good agreement with the experimental spectra-at the pentad level for the carbonyl signal and at the tetrad level for beta-CH2 signal.