The coexistence curves and light scattering data for a critical solution of benzonitrile + octadecane have been reported. The critical exponents relating to the difference in density variables of two coexisting phases beta, the correlation length nu, and the osmotic compressibility gamma have been calculated. The experimental results of the coexistence curves have also been analyzed to examine the Wegner correction terms and the behavior of the diameter of the coexistence curves. The data analysis shows that the 3D-Ising behavior is valid in a temperature range close to the critical point. However in a wide temperature range the exponential values of nu and gamma change with the temperature significantly, clearly exhibiting the critical crossover from the 3D-Ising universality class to the classical one. (C) 2005 Elsevier Ltd. All rights reserved.