In this study, the binding of a basic dye such as basic brown 1 [BB 1] onto a crosslinked poly(N-vinylpyrrolidone) [CPVP] was investigated. Adsorption of the azo dye onto the CPVP was studied by the batch adsorption technique at 25 degrees C. In adsorption experiments a Langmuir type (L) adsorption was found with respect to the Giles classification system. Binding parameters such as initial binding constant (K-i), equilibrium constant (K), monolayer coverage (n), site-size (u), and maximum fractional occupancy (<(theta)over cap>), and thermodynamic parameters such as heat of adsorption (Delta H), free energy of adsorption (Delta G) and entropy of adsorption (Delta S) for the CPVP/BB 1 system were calculated by using Klotz, Scatchard, and Langmuir linearization methods.