Measurements of the spatial contrast sensitivity function and orientation selectivity of visual neurons in the foveal striate cortex (V1) of primates were interpreted within the context of a model of the two-dimensional spatial structure of their receptive fields. Estimates of the spatial dimensions of the receptive fields along the axis of preferred orientation were derived from the application of the model and were compared with estimates of the smallest spatial subunit in the dimension orthogonal to the preferred orientation. Some measure of agreement was found with corresponding estimates of parameters for psychophysical channels in human foveal vision.