We recorded the initial vertical vergence eye movements elicited in monkeys at short latency (~70ms) when the two eyes see 1-D horizontal grating patterns that are identical except for a phase difference (disparity) of 1/4 wavelength. With gratings composed of single sine waves, responses were always compensatory, displaying Gaussian dependence on log spatial frequency (on average: peak=0.75 cycles/deg; SD=0.74; r²=0.980) and monotonic dependence on log contrast with a gradual saturation well described by the Naka-Rushton equation (on average: n=0.89; C₅₀=4.1%; r²=0.978). With gratings composed of two sine waves whose spatial frequencies were in the ratio 3:5 and whose disparities were of opposite sign (the 3f5f stimulus), responses were determined by the disparities and contrasts of the two sine-wave components rather than the disparity of the features, consistent with early spatial filtering of the monocular inputs prior to their binocular combination and mediation by detectors sensitive to disparity energy. In addition, responses to the 3f5f stimulus showed a nonlinear dependence on the relative contrasts of the two sine waves. Thus, on average, when the contrast of one sine wave was 2.3 times greater than that of the other then the one with the lower contrast was largely ineffective as though suppressed and responses were determined almost entirely by the sine wave of higher contrast: Winner-Take-All. These findings were very similar to those of Sheliga et al. (2006a; 2007) on the vertical vergence responses of humans, indicating that the monkey provides a good animal model for studying these disparity vergence responses.