This study compared the fixation disparity curve parameters obtained with the Wesson fixation disparity card, the most commonly used method, to those of the Saladin fixation disparity card, a new device. We measured the fixation disparity parameters for 36 subjects who were in their twenties(average 22.39±1.98 years old) who had a monocular best-corrected visual acuity of 18/20 or better, had no strabismus as determined by cover test, had no vertical phoria by the Maddox rod method, and had no ocular history. The x-intercepts were shifted in the base-in direction with the Wesson card than Saladin card( -3.58±3.2, p = 0.000), the y-intercepts were shifted in the exo direction with the Wesson card than the Saladin card( -5.44±6.0, p = 0.000), the slope of fdc with the Wesson card was steeper than the slope obtained with the Saladin card( -1.02±1.36, p = 0.001). The differences were statistically significant for 17 exophores but not for 7 esophores. Type I fixation disparity curves were most common and type III were the next with the Wesson card. The fixation disparity curve parameters measured with these two instruments are different. So fixation disparity curve parameters obtained from one of these instruments cannot be used with normative findings from the other.