The objective of this study was to investigate the rheological properties of the light crude oil and its emulsions in order to obtain more knowledge about the rheological behavior of oil flow in pipelines. The experiments were carried out at a temperature of 20 degrees C by using the RS600 RheoStress (ThermoHaake, Germany). The results showed that the viscosity of the prepared emulsions varied with their water contents. In the case of 100% light crude oil, the study of the functional relationship demonstrated the quasi-Newtonian behavior with a moderate constant viscosity. However, for emulsions with different water concentrations, their rheological behaviors were described in better way by the Ostwald de Waele and the Herschel-Bulkley models. The stability of emulsions was identified by measuring the rheological properties including non-Newtonian viscosity, the elastic modulus, (G'), the loss modulus, (G ''), the phase angle (delta) and the complex viscosity (eta*). The results indicated that the rheological properties and the physical stability of emulsions were significantly influenced by the water contents and the nature of crude oils. (C) 2011 Elsevier Ltd. All rights reserved.