Acrylic acid-vinyl acetate copolymers were prepared in bulk using benzoyl peroxide as initiator. Copolymer compositions were determined by volumetric titration; monomer reactivity ratios were determined by the method of Kelen-Tüdös. Terminal and penultimate reactivity ratios have been calculated using the observed monomer triad sequence distribution determined from 13C-NMR spectroscopy. Triad sequence distribution was used to calculate dyad concentrations, probability parameters, number-average sequence lengths and comonomer mol fractions in the copolymers. The observed triad sequence concentrations as determined from 13C-NMR agreed well with those calculated from reactivity ratios.