The sizes of nuclei obtained during the condensation of gold on UHV-cleaved mica substrates were measured as a function of time of exposure to the incident flux. The size distributions obtained were symmetrical and initially sharply peaked, but flattened and broadened with increasing time of condensation. The mean size, always well defined with a few angstroms, was found to vary approximately as t1/3, provided the number density of nuclei remained nearly constant. When the number density of nuclei increases, the growth rate is suppressed. The time taken to reach a given size increases with increasing temperature when the nuclei are growing as isolated particles. When the nuclei are spaced such that their diffusion fields overlap, then the time taken to reach a given size decreases with increasing temperature. The rms diffusion distance could be defined rather precisely giving (ΔGdes–ΔGsd)=0.5(±0.05) eV.