The relative viscosity of dispersion was investigated focussing the attention on the drop size distribu-tion as well as the volume concentration of the dispersed phase:
μ_r = exp[AФ_t + BФ_t²]
where Ф is the volume concentration of the dispersed phase; A and B are functions of drop size distribution of the diis-persed phase and viscosities of the continuous and the dispersed phases. In order to validate the proposed model, published data were applied to the model and were compared with cal-culated results. The errors between experimental viscosities and calculated values ranged from 0% to 3.86% depend-ing on the materials of dispersions. Also the same model has been applied to the emulsion system. Predicted viscos-ities of emulsions by the model agreed with experimental data reasonably well giving a maximum error of 4.1%.