Following the successive presentation of two masking gratings (M1 and M2), subjects were required to detect the presence or absence of a single vertical line (TS). When the orientations of the two masks were optimal, M1 was able to reduce the masking effect of M2 on the TS. For a vertical TS, disinhibition was maximal when the orientations of M1 and M2 were similar and was minimal when the orientational difference was greater than 15 deg. It is suggested that the spatial selectivity of the disinhibition function reflects the activity of neurons tuned to orientation, and that the disinhibition masking paradigm may be a useful psychophysical technique to measure tuning functions of other feature detectors.