Organic materials found in natural waters are, for the most part, humic substances, i.e., humic acid, fulvic acid, and humins. Humic substances are the cause of the yellow or brown color imparted to waters with high organic content. This article discusses the removal of color from drinking water with the use of aluminum sulfate as a coagulant. Optimum areas of color removal during the coagulation process were studied in a series of jar tests and diagrammed as an aid to the design and operation of water treatment plants. The mechanisms for the removal of color associated with humic acids seem to be closely associated with the removal of turbidity. Includes 13 references, figures.