In this article a simple and effective algorithm is introduced for the system identification of the Wiener system using observational input/output data. The nonlinear static function in the Wiener system is modelled using a B-spline neural network. The Gauss-Newton algorithm is combined with De Boor algorithm (both curve and the first order derivatives) for the parameter estimation of the Wiener model, together with the use of a parameter initialisation scheme. Numerical examples are utilised to demonstrate the efficacy of the proposed approach. (Billings and Fakhouri 1979;Stoica and So¨derstro¨m 1982;Greblicki and Pawlak 1986;Greblicki 1989Greblicki , 2002Lang 1997;Verhaegen and Westwick 1996;Bai and Fu 2002;Chen 2004;Chaoui, Giri, Rochdi, Haloua, and Naitali 2005;Hong and Mitchell 2007). Alternatively, the Wiener model comprises a linear dynamical model followed by a nonlinear static functional transformation. This is a reasonable model for any linear systems with a nonlinear measurement device, or some industrial/biological systems (Hunter and Korenberg 1986;