A detailed theoretical study of the radiative properties of water droplet and ice clouds at visible and infra-red wavelengths of 2.3, 3.5, 3.8 and 8.5 and 11 pm is presented. The radiative transfer computations have used a model atmosphere in which the microphysical properties of the clouds have been accurately incorporated. A range of physically realistic size distributions for the cloud particles have been used. The