Fundamental data, including density and rheological behavior, of nitrile butadiene rubber in solutions of monochlorobenzene and o-dichlorobenzene were investigated, under a wide range of experimental conditions, including operation temperatures and polymer concentrations up to 165degreesC and 20% (wt), respectively. Shear rates of up to 1300/s were used for the measurement of rheological behavior. Within the range of the operational conditions employed, the solutions of nitrile butadiene rubber show Newtonian fluid behavior. A characteristic viscosity is proposed as a model parameter to correlate the viscosity of the NBR solutions. As a result, empirical correlation equations for density and viscosity are formed. The purpose of this work is to provide fundamental data for process development of the solution hydrogenation of nitrile butadiene rubber.