In a uniform rotating liquid of uniform depth, Kelvin waves may be propagated in one direction along a straight boundary of the liquid. The Wiener-Hopf technique is used to obtain the wave field due to Kelvin waves incident at a rightangle corner. An asymptotic solution is obtained for the field far from the corner. It is shown that for low frequencies the Kelvin waves are propagated round the corner without change of amplitude, but that for high frequencies cylindrical waves of the ‘Poincaré’ type are generated at the corner, so that the amplitudes of the Kelvin waves propagated round the corner are reduced.