Ultrafine amorphous alloy particles (UAAP) constitute an overlapping area of amorphous alloys and nanophase materials. Special properties of the particles derived from the combination of their long-range disordered structure and nanoscale size are of great interest in catalysis. This paper reviews some fundamental aspects in the chemical preparation of UAAP consisting of transition metal (M) and metalloid elements (B, P) and their applications in catalysis. The three fundamental reaction equations in the preparation of MB UAAP, the autocatalytic nature of the chemical reaction to produce NiP UAAP, and a milling-induced solid state reduction method are discussed. Their interesting catalytic properties, especially their unique selectivities in some of the hydrogenation reactions, have shown promising potential applications of UAAP in catalysis. With regard to the interactions between the transition metal and metalloid elements of the UAAP, experimental results and theoretical calculations have led to the suggestion that the charge transfers between M and B or P are in the same direction but to different extents, i.e., from metal to metalloid elements.