The paper presents a comparative analysis of the non-linear dielectric and viscometric studies of the liquid systems: acetone/cyclohexane, acetone/decahydronaphthalene, nitrobenzene/cyclohexane and nitrobenzene/decahydronaphthalene. All these systems reveal precritical-like behaviour (in specific ranges of temperatures and concentrations) manifested by a characteristic maximum on the curve of the concentration dependence of the non-linear dielectric effect parameter (Delta epsilon/E-2). The concentrations corresponding to the maxima of Delta epsilon/E-2, x 20.35 for acetone in cyclohexane, x congruent to 0.55 for acetone in decahydronaphthalene, x congruent to 0.3 for nitrobenzene in cyclohexane and x congruent to 0.42 for nitrobenzene in decahydronaphthalene, which seems to indicate a significant steric effect (not only) of the solvent molecules. For the solutions of nitrobenzene in cyclohexane and in decahydronaphthalene and for acetone in cyclohexane, the curve of the activation energies of viscosity as a function of concentration also reveals maxima close to the concentrations of the maxima of Delta epsilon/E-2. (c) 2005 Elsevier Ltd. All rights reserved.