Field problem surveillance for the Army has identified vehicle power loss caused by premature fuel filter plugging as a major maintenance and readiness problem. A systematic approach to the analysis of fuel system contaminants has been partially developed. First, a set of reference materials was gathered based on the most commonly encountered fuel system contaminant. The most useful microscopic and spectroscopic techniques and their utility for examining the various types of contaminants were identified. The individual reference materials were characterized for use in comparison to actual field samples. Sample preparation procedures were developed for fuel filters, fuel samples, and fuel tank sludge samples. A scheme for the final analysis of the prepared samples was devised. This methodology requires some technical judgment in assessing the relative amounts of some of the contaminant types; however, this methodology provides a step-by-step means of determining the identify of fuel system contaminants.