The effects of different disparities on the global stereopsis were examined by measuring the cumulative time of stereopsis as an index, using 13 complex ambiguous stereograms. It was found that the difficulty for stereopsis increased, (a) as the number of boundaries between different disparities increased, (b) as the spatial separation between the boundaries decreased, or (c) as the difference between the two disparities increased. These effects were also studied in relation to other factors such as noise and magnitude of disparity which might also be important for global stereopsis.