If a cell is to serve as a depth detector in a local stereopsis mechanism, it could indicate the depth of a specific object feature by responding only when that feature is located at the cell's preferred depth and being silent at other depths, the preferred depth varying from cell to cell over a small range. In order to assign a depth value to a particular object feature, the two receptive fields of the cell should respond to one and the same feature in the visual field. This can be done only if the organizations of the two receptive fields are identical or nearly so. Out of 31 cells in the simple family in the cat striate cortex, 15 were selected as having a monocular response from each eye sufficient to be able to examine their receptive field organizations in quantitative detail. The two receptive fields of each cell were remarkably similar in respect to the number, spatial sequence and position disparities of the response peaks to moving light and dark bars, as well as in respect to the relative ocular dominances, peak separations and direction selectivities of the response peaks to the two kinds of bar.