A study was made of the flow patterns in a capillary rheometer barrel to determine if there were any phenomena which might affect viscosity determinations. The rheometer barrel was loaded with layer of several different colors of the same plastic. Various percentages of the initial charge were extruded through the capillary using normal techniques at various shear rates and temperatures. At the end of each test, the material remaining in the barrel was frozen and removed as a plug. The plugs were then sectioned and a flow diagram was constructed by measuring the colored layers. Although the expected laminar flow was observed, upward flow at the wall and channeling at the center were also evident. These phenomena were noted even when only a small portion of the charge had been extruded through the capillary. This paper presents these findings in detail, picturing the flow patterns observed and illustrating the effects of temperature and shear rate.