A planar array of longitudinal shunt slots in rectangular waveguides has been designed to produce a CSC squared theta. COS theta patter in the E-plane and -22-dB side lobes in the H-plane. The array operates at 15 GHz. The choice of E-plane amplitude and phase distribution, to synthesize the CSC Theta. COS theta pattern shape over the sector 8 degrees to 50 degrees below broadside, involved a tradeoff study. The widely used Woodward approach of superimposing a family of uniform-amplitudeuniform-progressive-phase distributions on the aperture was studied but not used in preference to a technique reported by Elliott of perturbing the roots on a Chelkunoff unit circle to obtain the desired pattern shape. Twelve roots were perturbed in a systematic way to obtain an optimum amplituude distribution with accompanying phase angles. The paper also describes a method used to spread the resultant E-plane distribution and the H-plane Taylor distributioon over a circular aperture. The mutual coupling between elements was taken inot account for the design. The predicted results show good agreement with measurements.