Laboratory batch cylinder tests are commonly used to assess the effectiveness of flocculants to enhance the settling rate of suspensions. In this paper, the performance obtained from batch cylinder tests is compared to that from a new flocculation system based upon vertically mounted, concentric rotating cylinders (Couette geometry). It has been shown that the results from batch cylinder tests are very dependent upon factors such as the number of inversions and the cylinder diameter. These limitations are overcome by conducting flocculation in a continuous mode under reproducible mixing conditions such as prevail within a mechanically driven Couette device. Results obtained with this equipment are found to be of much higher reproducibility than from cylinder tests conducted under set conditions.