We consider the diffraction problem of a scalar plane wave incident upon an array of semi-infinite cylinders whose parallel axes lie at the vertices of a regular polygon. For the Dirichlet boundary condition and under the assumption of small radii and large inter-element spacings, an exact solution to the problem is obtained by means of the Wiener-Hopf technique. Far field expressions are derived and the approximate evaluation of some difficult integrations given. Results are presented for axial incidence on double, triangular and square arrays.