Results of dynamic light scattering experiments are reported which demonstrate that the mutual diffusion coefficient of 2-butoxyethanol/water mixtures of noncritical composition exhibits a characteristic temperature and composition dependence : The diffusion coefficients of the two phases of noncritical composition coexisting along the liquid/liquid coexistence curve decrease by an order of magnitude in the temperature range (T-p-T-c)< 10 K approaching the lower critical point (T-p, temperature of phase separation; T-c, critical temperature). In the homogeneous 1-fluid phase region of the phase diagram, the D vs (T- T-p) curves of mixtures of noncritical composition are shifted to smaller values of D with decreasing values of y-y(c) (y, mass fraction of 2-butoxyethanol; y(c), critical mass fraction). These findings are discussed on the basis of the model of regular mixtures.