The literature indicates that over twenty different tests have been used for the purpose of evaluating the coagulation of turbidity in water treatment. Five of these tests were selected for study as they were felt to be basic and/or particularly important. These include: residual turbidity, filtered turbidity, refiltration, colloid titration, and a continuous pilot scale filter process. The five methods were compared holding all variables other than pH and alum dose constant. While some tests were shown to strongly correlate with others, the results of the refiltration technique were found to be biased in favor of low alum concentrations, and the colloid titration test was found to lack sensitivity with respect to variations in alum dosage but was quite sensitive to pH changes. The practical implications of this study suggest that water treatment plants should follow guidelines given for choosing the most useful test for their process.(Author)