Nanocrystalline FeAs, CoAs and NiAs were prepared by keeping the mixture of FeCl3, CoCl2 or NiCl2 with arsenic and KBH4 in ethylenediamine (en) at 100 degrees C for 4 h, respectively. X-Ray powder diffraction (XRD) patterns and transmission electron microscope (TEM) images show that the products are orthorhombic FeAs, CoAs and hexagonal NiAs, respectively, and all are well crystalline in nanometers.