Two Au/NaHY systems examined by TEM were prepared using an autoreduction method of Au3+ by its ethylene diamine ligands. When about 10% of the cations are H+ the particle diameter distribution is found to be about 2 nm and homogeneous. If 75% of cations are H+ the gold particle distribution is centered around 3-4 nm. Gold particles are of good stability when exposed to H-2 at 573 K for two days and the stability under O-2 greater with the higher acidified zeolite.