The synthesis of omega-hydroxy hexathiolate-protected subnanometric gold clusters is described. Quantitative high-angle annular dark-field scanning transmission electron microscopy has been employed to determine atomic composition. The smallest particles observed contain 13 +/- 2 Au atoms; all others contained multiples of this particle size. The UV-vis spectra show the bands of discrete electronic transitions for this core size. Chemical analyses indicate a composition of Au-13(SC6OH)(8) for the clusters. The role of the ligand shell in determining the core size is highlighted.