The purpose of this study was to establish a practical basis of comparison among three clinical tests designed to measure an observer's spatial contrast sensitivity function (CSF): the AO contrast sensitivity test plates (Arden grating test), the Vistech VCTS 6500 chart, and the Nicolet CS-2000 contrast sensitivity testing system (Optronics system). Each test was administered under standard conditions to a randomly selected subset of 71 normal observers. Scores were converted to absolute contrast and spatial frequency units for comparison. Results were similar for all three tests at intermediate and high spatial frequencies, but at low spatial frequencies the Vistech and Optronics tests yielded significantly lower sensitivity scores than the AO plates. This discrepancy is probably due to area truncation.