In this study, the flow behavior of urethane oils prepared with different reactant ratios was determined. For this purpose, in the first step, the viscosities of polymer solutions were determined at different temperatures. Then, Bingham, Power-law and Casson models were tested to express the relationship between r and gamma. Under test conditions, toluene diisocyanate (TDI)-based polymer solutions behaved as non-Newtonian fluids, whereas the polymer solution prepared from poly(1,4-butandiol) tolylene 2,4-diisocyanate terminated prepolymer (PBTDI)-based samples behaved as Newtonian fluids. Additionally, Andrade and Erickson's equations were tested for investigating the viscosity-temperature and viscosity-concentration relationships, respectively. It was showed that, these equations were available for all polymer solutions. After comparing all results with those of comparative sample we suggested that, the polymer solution prepared from the sample containing high ratio of TDI, could be used in the high solid coating formulation for industrial application. (C) 2004 Published by Elsevier B.V.