THIS PAPER DESCRIBES THE USE OF VSA (VARIATION SIMULATION ANALYSIS) AUDIT TO SEPARATE SOURCES OF BUILD VARIATION IN AN ASSEMBLY OPERATION. VSA AUDIT ISOLATES THE EFFECTS OF COMPONENT VARIATION FROM VARIATION INCURRED DURING THE ASSEMBLY PROCESS BY USING MEASURED COMPONENT DIMENSIONS IN A COMPUTER SIMULATION OF THE ASSEMBLY PROCESS. VSA AUDIT IS A TOOL WHICH HIGHLIGHTS DIFFERENCES BETWEEN THE ASSEMBLY OPERATION AND AN IDEAL BENCHMARK OF THE ASSEMBLY PROCESS. SIGNIFICANT DIFFERENCES BETWEEN THE VALUES OF VSA AUDIT PREDICTIONS AND OBSERVED VARIATIONS INDICATE DIFFERENCES BETWEEN THE IDEAL AND ACTUAL ASSEMBLY PROCESSES. THE NATURE OF THIS DEVIATION MAY BE INVESTIGATED USING THE VSA MODEL TO SIMULATION TOOL WEAR, BREAKAGE OR OTHER POTENTIAL SOURCES OF VARIATION IN THE PROCESS. AN EXAMPLE OF A SIMPLE ASSEMBLY WILL FORM THE BASIS FOR A DISCUSSION OF THE VSA AUDIT APPROACH, ITS STRENGTHS, WEAKN