The purpose of this study was to evaluate the display performance of the liquid crystal display monitors according to the American association of physicists in medicine task group 18 (AAPM TG18) protocol at prior and after new calibration. We measured minimum and maximum luminance, luminance ratio, luminance and contrast response, luminance angular and spatial dependency, resolution, veiling glare and chromaticity quantitatively for 33 medical displays. Display noise was evaluated only visually. The mean maximum luminance and luminance ratio were 386 and 273 cd m(-2), respectively. The mean deviation of measured luminance and contrast response from expected response associated with the digital imaging and communications in medicine (DICOM) grayscale standard display function (GSDF) were 9.76 and 2.35 % at prior calibration and 1.23 and 0.26 % after recalibration, respectively. In luminance uniformity test the mean maximum luminance deviation was 16 %. Luminance method was used in the spatial resolution test and the mean percent luminance difference was 12 % at the center. The mean glare ratio was 1 154. The average color uniformity parameter across the display area of each display device was 0.0093. Majority of the test results were in good agreement with the criteria recommended by AAPM TG18 report. Considerable improvement was observed in display luminance and contrast response with respect to expected response of DICOM GSDF after new calibration for some displays.