Small PVP-stabilized gold clusters were successfully prepared by the homogeneous mixing of continuous flows of aqueous AuCl4- and BH4- in a micromixer. Spectroscopic characterization revealed that microfluidic synthesis could yield monodisperse Au:PVP clusters with an average diameter of similar to 1 nm, which is smaller than clusters produced by conventional batch methods. These similar to 1 nm Au:PVP clusters exhibited higher catalytic activity for the aerobic oxidation of p-hydroxybenzyl alcohol than did Au:PVP clusters prepared by batch methods.