This chapter reviews the kinds of indications that reveal a developing wear problem. These involve the human senses of sight, hearing, smell, and touch. Tribosystem analysis is basically a process to dissect and organize the mechanical, chemical, thermal, and materials-related aspects of a wear-related and/or friction-related condition. Some wear problems involve cosmetic indications because the function of some products includes how they look to the user. Visual inspection and surface imaging are among the most common ways to detect and assess the relative severity of wear problems, but sometimes, the worn surface is not visible without disassembly of the problem component. While vibration monitoring is used to detect problems in numerous engineering tribosystems, other sources of sound besides periodic vibrations can help diagnose wear and friction issues as well. Oil analysis is an extensive subject whose focus can be subdivided into fluid composition and thermophysical properties, external contamination level, and tribosystem-generated wear debris.