In this study, poly(2-acrylamido-2-methyl-1-propane sulfonic acid-co-1-vinyl-2-pyrrolidone), P(AMPS-co-VP), hydrogels were prepared by free radical cross-linking polymerization method in deionized water at 60 degrees C for 24 hours with different molar percentages of AMPS and VP. In the preparation of hydrogels, ammonium persulphate (APS), N, N'-methylenebisacrylamide (NMBA) and N, N, N', N'-tetramethylethylenediamine (TEMED) were used as initiator, cross-linking agent and accelerator, respectively. NMBA was used in amounts of 5, 6 and 8% with respect to total monomer concentration in the feed. The equilibrium swelling value (ESV) of P(AMPS-co-VP) hydrogels was determined in deionized water and in buffers with different pH values. ESV of P(AMPS-co-VP) hydrogels prepared with 5% NMBA is higher than that of the counterparts with 6 and 8%. Swelling behavior of hydrogels was strongly dependent on AMPS content and ESV decreased with increase in AMPS amount. An evident pH-sensitivity was not observed for the P(AMPS-co-VP) hydrogels. The characterization study was performed using Fourier transform infrared spectroscopy and thermogravimetric analysis.