The American Association of Physicists in Medicine Task Group 18 (TG18) has recently developed guidelines for objective performance evaluation of medical displays. This paper reports on the first multi-institutional trial focusing on the implementation and clinical verification of the TG18 methodology for performance testing of medical image display devices in use at different clinical centers. A minimum of two newly-installed PACS display devices were tested at each institution. The devices represented a broad spectrum of makes and models of 1-5 megapixel CRT and LCD display devices. They were all either new or in clinical use for primary diagnosis with acceptable performance at the time of testing. The TG18 test patterns were loaded on all the systems. Visual and quantitative tests were performed according to the guidelines for assessing specific display quality characteristics including geometrical distortion, reflection, luminance response, luminance uniformity, resolution, noise, veiling glare, color uniformity, and display artifacts. The results were collected in a common database. For each test, the results and their variability were compared to the recommended acceptance criteria. The findings indicated that TG18 tests and guidelines can easily be implemented in clinical settings. Most recommended criteria were deemed appropriate, while small minor modifications were suggested.