Capillary rheometers have been widely used in the study of the rheological behavior of thermoplastics but their application to rubber has so far been Limited, An investigation was therefore carried out to determine the effect of mastication and temperature oil the rheological properties of natural rubber using a capillary rheometer. The flow of the rubber in the barrel of the capillary rheometer was observed at various lest conditions such as die geometry, piston speed, and test temperature using layers of pigmented rubber compound, this involving the use of a split barrel system. It was round that the flow patterns in the barrel of the capillary rheometer used were very complex and were a function of piston displacement.