To study the binocular vision deficits associated with anisometropia, monkeys were reared with alternating monocular defocus, which allowed monocular mechanisms to develop normally while binocular mechanisms were selectively compromised. A defocusing contact lens of -1.5 D, -3 D, or -6 D was worn on alternate eyes on successive days (n = 3 per lens power) from 3 wk to 9 mo of age. The control subjects were two normally reared monkeys and two human observers. Functional binocular vision was assessed through behavioral measurements of stereoscopic depth discrimination thresholds as a function of spatial frequency. To characterize the extent of the deficits in disparity processing at a given spatial frequency, the contrast required to support stereopsis was determined for a range of disparities that exceeded the subjects' measured stereoacuity. The lens-reared monkeys showed spatial-frequency-selective deficits in stereopsis that depended on the magnitude of the simulated anisometropia experienced during the rearing period. For a given spatial frequency, the treated monkeys generally required higher than normal contrasts to support stereopsis even for large disparities. Moreover, a given increase in contrast produced smaller than normal improvements in stereo discrimination in our treated subjects, which suggests that in addition to deficits in contrast sensitivity, disparity-sensitive mechanisms exhibited low contrast gains. The spatial-frequency selective nature of the binocular deficits produced by the imposed anisometropia indicate that disparity processing mechanisms are normally spatial-frequency selective and that mechanisms tuned to different spatial frequencies can be differentially affected by abnormal binocular visual experience.