We describe the solution growth of a series of discrete sized generations of Au nanoparticles by the heterogeneous deposition of atoms onto monodisperse seed nanocrystals. The growth process was studied using size-exclusion chromatography (SEC) and transmission electron microscopy (TEM). The size dispersion of each generation was determined from the SEC elution line widths and the spectral homogeneity of the elution peaks. The heterogeneous deposition of various amounts of Ag on Au nanocrystals and Au on Ag nanocrystals using the same synthetic protocol is also described. The effect of such deposition on the optical absorbance of each generation of larger clusters was measured during SEC using an on-line photodiode array absorbance detector.