1. Grating patterns were used to obtain a quantitative description of cells in the visual cortex of the cat whose response amplitude depended critically upon the orientation of the moving grating.2. In all such cells the impulse frequency was found to decrease linearly with angle on either side of an optimum angle (the preferred angle) until the response fell to zero or to a base frequency. The angular rate of change of response varied between cells and was expressed as the half-width at half amplitude (the angular selectivity).3. The angular selectivity of thirty-five cells was determined and more than half (nineteen) of these fell within the range 14-26 degrees .4. Fourteen cells responded optimally only when the grating was moved in one direction. Twenty-one cells responded optimally to two directions of movement 180 degrees apart, but the response in the two directions was not always equal.5. No significant correlation was found between the response amplitude at the optimum angle and the angular selectivity.6. The distribution of preferred angles did not show any difference between the oblique orientations and the vertical and horizontal orientations.7. These results are compared with a previous psychophysical estimate of angular selectivity.