The solubility parameters of pure Poly(n-vinyl 2-pyrrolidone) (PVP) and Poly(n-vinyl 2-pyrrolidone/ethylene glycol dimethacrylate)P(VP/EGDMA) hydrogels have been evaluated via swelling experiments. Twenty solvents with various solubility parameters have been used in the swelling experiments. Considering the limitations of using the approach as developed by Gee, we have applied an asymmetric double sigmodial equation for locating the peak maxima in swelling curves. The solubility parameters are evaluated via this new approach. The solubility parameter of pure PVP is determined to be 11.38 +/- 0.11 Kb. The incorporation of EGDMA into the gel system slightly reduced the solubility parameter. The influence of relative amount of EGDMA on the solubility parameter was investigated, and evaluated values compared with literature and theoretically determined solubility values by group contribution values of van Krevelen, Small, and Hoy.