We fabricated gold nanoparticles on nanoporous silicon microparticles using electroless deposition in a hydrofluoric acid solution containing gold chloride. The reaction was followed by UV spectrometer analysis of the absorbance of the solution (proportional to the nanoparticle concentration) for two temperatures (20 and 50 degrees C). The results indicate that the process is autocatalytic, described by a pseudo-first-order reaction, the apparent rate constant k(obs) of which was determined by utilizing UV spectrometer data. We found that the reaction rate constant at 20 degrees C is 7 x 10(-3) s(-1) and that at 50 degrees C is 2.9 x 10(-2) s(-1). Scanning electron microscope (SEM) analysis of samples and diffusion-limited aggregation (DLA) simulations were used to validate the results. This study aims to resolve the kinetics of the electroless deposition of gold on silicon at the nanoscale, in the present state of art missing a quantitative characterization, for certain conditions of growth and given values of temperature and concentration of the reagents. Results may have applications to the synthesis of gold nanoparticles and their use as nanosensors, drug delivery systems, or metal nanometamaterials with advanced optical properties.