Rotational molding is one of the most important methods for the manufacture of hollow plastic products. However, there are several unsolved problems that confound the overall success of this technique. Part warpage caused by inappropriate mold design and processing conditions is one of them. An experimental study is reported on the effect of different processing factors on the warpage of rotationally molded parts, including part thickness, oven temperature, cooling condition, mold material, mold release, colorant, fiber reinforcement, foaming and mold pressurization. Experiments were carried out on a lab-scale rotational molding unit. After molding, the part warpage was measured by a profile-meter. It is shown that the mechanisms of warpage formation and removal can be explained and, this being done, steps can be taken to ensure that the warpage is minimized. This provides significant advantages in terms of reduced cycle time and improved product quality.