Relaxation of disclination loops created during shear flow of a low molar mass and a polymer liquid crystal were monitored using a special shear stage with a videomicroscope. Loops in the polymer system generally displayed initially highly distorted contours. In the small molecule liquid crystal, the loop contours consistently exhibited very simple, generally convex shapes. In the polymer system, the complex line shape reflects the many prior loop-loop coalescence events due to the greater density of loops than in the small molecule system. Sequential images of loops were analysed to determine the velocity of the disclination loops as a function of the local curvature. Observations and simulations indicate that local disclination line curvature is a driving force in loop evolution. The reduction of regions of high loop curvature is inherently slower in the polymer liquid crystal due to the higher viscosity. In addition, the motion of the disclination contour at very high values of curvature in the polymer liquid crystal is slowed due to the presence of lower molecular weight components at the defect core which themselves must diffuse along with the line defect.