The uniform compression of laser irradiated spherical targets to thermonuclear conditions places exacting requirements on the uniformity of energy deposition. This issue is currently under investigation with the 4 kJ, 24-beam OMEGA laser facility operating at 1.05 μm with 1 ns pulses. Estimation of the irradiation uniformity is made in terms of the amplitudes of specific low order spherical harmonic modes, deduced from precise characterization of the individual beam target intensity profiles. The factors which influence these beam characteristics, and the adoption of measures to improve the overall uniformity are discussed.