Quantum size silver particles down to 2 nm were prepared by reducing the silver ions directly at the silver arachidate monolayer-aqueous subphase interface with hydrazine and for which a rectangular trough with three compartments designed in our laboratory was employed. The silver particles formed in situ at the monolayer surface at adequate pH conditions are approximately uniform in size and this can be attributed to the presence of a monolayer matrix. The surface force of the monolayer matrix inhibits the aggregation of small particles during their growth as well as during their preservation and the stability of small particles is markedly improved. Brewster angle microscopy was applied to study the growth kinetics of silver particles formed in situ at the monolayer surface and the effect of pH on the rate of silver growth is discussed.