Mutual diffusion coefficients (interdiffusion coefficients) and molar conductivities have been measured for copper(II) chloride in water at 298.15 K and 310.15 K at concentrations between 0.005 mol(.)dm(-1) and 0.05 mol(.)dm(-3). The diffusion coefficients were measured using a conductometric cell. The experimental data are discussed on the basis of the Onsager-Fuoss model. The Nernst diffusion coefficients derived from diffusion (1.297 x 10(-9) and 1.690 x 10(-9)) M(2.)s(-1) and from conductance (1.282 x 10(-9) and 1.663 x 10(-9)) M(2.)s(-1) at two temperatures (298.15 K and 310.15 K, respectively) are in good agreement.