The free radical copolymerization of N-methylolacrylamide(M₁) with styrene (M₂) was studied in three different kinds of solvents(ie., dimethyl sulfoxide, ethanol, and dioxane) at 70℃ using α, α''-azobisisobutyronitrile as an initiator. The monomer reactivity ratios by Kelen-Tudos method were calculated as follows : Dimethyl sulfoxide, r_l=0.12, r₂=2.59 ; Ethanol, r₁=0.29, r₂=1.28 ; Dioxane, r_l=1.30, r₂=1.35. A strong influence of solvent on the monomer reactivity ratios was observed, and the effect of solvent upon the N -methy lolacrylamide was confirmed by the shift of the peaks corresponding to the amide carbonyl and amide N-H group in the infrared spectra of the solution. The greater is the shift in the C=O absorption peak towards lower wavenumber (ν), the smaller is the amount of the N -methylolacrylamide in the prepared copolymers. It can be concluded with these results that the hydrogen bonding and dipole-dipole interaction depending on the nature of solvents (polarity, dielectric constant etc.) could affect the polarity and reactivity of the double bond in the N-methylolacrylamide.