Copolymers of vinyl pyrrolidone (VP) and the methacrylic monomers derived from salicylic acid, 2-hydroxy-4-methacrylamidobenzoic acid (4HMA) and 2-hydroxy-5-methacrylamidobenzoic acid (5HMA), were prepared by free radical pnlymerization in DMF solution at 50 degrees C, using 2,2'-azobisisobutyronitrile (AIBN) as initiator. The reactivity ratios of the monomers were calculated according to the general equation using the Fineman-Ross and Kelen-Tudos linearization methods, and also the Tidwell and Mortimer nonlinear least-squares treatment. The most probable reactivity ratio values derived from the 95% confidence diagram were the Tidwell and Mortimer ones giving r(4HMA) = 6.59 and r(VP) = 0.03 for the 4HMA-VP system, and r(5HMA) = 10.58 and r(VP) = 0.02 for the 5HMA-VP copolymer. The micro-structure of the copolymer chains was analysed according to a first-order Markov statistic and to the Skeist equation for the dependence of the composition on the conversion degree.