It is shown that the resolution of an analogue-to-digital converter may be improved by the addition of random noise to its input. To achieve the improvement, successive measurements of the input must be made and the results averaged. The increase in resolution possible is calculated for various noise levels. For example, a resolution of 2 Δ without noise is improved to better than 0.1 Δ and 0.01 Δ by r.m.s. noise levels of about 0.75 Δ and Δ, respectively. Integrating gates wider than the correlation time of the noise require higher noise levels to achieve the same improvement in resolution as narrow gates.