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Elastohydrodynamic lubrication (EHL) film thickness suggests the capability of a lubricant to support load under a set of hydrodynamic conditions. It is related to the rheological properties of a lubricant, contact geometry, materials properties, and operating conditions such as load, speed, and temperature. Film thickness variation with speed or load may follow the prediction made with the theory of EHL. Experimental techniques based on capacity [1-3]; electrical conductivity and contact resistance [4-6]; discharge voltage [7]; X-ray transmission [8]; indirect laser transmission [9,10]; R-C oscillation technique [11]; and optical interferometry [12–35] have been used in EHL experiments for film- thickness measurement. On the other hand, as a result of the rapid development of high-speed computers, in-depth and detailed numerical analyses of EHL problems intend to become a routine practice. More influential factors can be considered now in EHL calculations: several non-Newtonian properties of a lubricant [30,31,36–38], surface roughness [32,33,37,38], the thermal effect [34,39,40], and non-steady-state transitions [35,41,42] have been included in a number of simulation models. Moreover, mixed lubrication simulations based on digitized real rough surfaces have been conducted in wider ranges of speed and load [36,37]. This section reviews and discusses the existing techniques for EHL film-thickness measurements, views of measurement data, and comparisons of measurement results with EHL simulation solutions.