THE IMPORTANCE OF WATER USAGE AND WATER TREATMENT TO THE WATERJET CUTTING INDUSTRY IS STATED, FOLLOWED BY A DISCUSSION OF THE PROBLEMS OF INADEQUATE WATER TREATMENT AND BENEFITS OF PROPERLY TREATED WATER. SEVERAL WATER TREATMENT PROCESSES ARE REVIEWED, INCLUDING FILTRATION, SOFTENING, DEIONIZATION, AND REVERSE OSMOSIS. GUIDELINES FOR EVALUATING WATER ANALYSIS ARE STATED AND DISCUSSED. CONCLUSIONS ARE DRAWN AS TO WHICH WATER TREATMENT PROCESSES ARE BEST FOR THE INDUSTRY. OWNING AND OPERATING COSTS OF VARIOUS WATER TREATMENT SYSTEMS ARE REVIEWED AND COMPARED. THE NEED FOR AN INDUSTRY-WIDE WATER QUALITY STANDARD IS SUGGESTED.