The development of stereoacuity for crossed and uncrossed disparities was assessed by means of a preferential looking procedure in a cross-sectional sample of infants aged 2-12 months and by following a longitudinal sample over the first 8 months of life. Crossed stereoacuity was found to develop earlier but at approximately the same rate as uncrossed stereoacuity. These data are consistent with the hypothesis that there exist two binocular mechanisms, one subserving disparity detection and one for uncrossed disparity detection.