We report optical scattering and birefringence observations on molten ultra-high-molecular-mass polyethylene (UHMMPE) and correlate these observations with a structure in the melt relating to the original reactor powder. In the quiescent state, pressure annealing can cause the observed light scattering to disappear; however, subsequent flow of the material causes the scattering to develop again. A simple microrheological model is proposed to explain some of the structure, pressure annealing and flow effects that have been observed.