IN THIS PAPER, FUNDAMENTAL ISSUES CONCERNING THE PERFORMANCE AND INTEGRITY OF WIRE AND NYLON/ABRASIVE FILAMENTARY BRUSHES ARE ADDRESSED. A DAMAGE CRITERIA FOR BRUSHING TOOLS IS ESTABLISHED ON THE BASIS OF IRREVERSIBLE INFLUENCES WHICH ALTER THE PERFORMANCE CHARACTERISTICS OF BRUSHES. TWO PRINCIPAL SOURCES OF DAMAGE ARE IDENTIFIED AND CONVENTIONAL METHODS OF ENGINEERING DESIGN ARE REVIEWED, WHICH ENABLE ONE TO ASSESS THE DAMAGE IMPARTED TO A BRUSH DUE TO SERVICE LOADS ENCOUNTERED DURING THE BRUSHING PROCESS. IN ADDITION, THE ROLE WHICH TEMPERATURE PLAYS IN THE DAMAGE OF NYLON/ABRASIVE BRUSHES IS EXAMINED AND DISCUSSED.