The growth of US nanoparticles during aging at ambient temperature is investigated with respect to the type of stabilizer, the concentration of the colloidal solution, and the molar ratio of sulfide to cadmium. The UV/Vis absorption spectra recorded within a period of seven days are analyzed by Karhunen-Loeve decomposition. It revealed a single process with first-order decomposition kinetics for each of the measured time series, and the respective rate constants are calculated. An explanation describing possible mechanisms for the observed ripening of the colloids is given. (C) 2003 Elsevier Science B.V. All rights reserved.