A series of copper selenides (CU2-xSe, CU3Se2 and CuSe) nanocrystals were prepared by a sonochemical method based on the reaction of copper acetate and sodium selenosulfate in an aqueous system. The phases and sizes of the nanocrystals could be conyrolled by changing the ratio of [Cu2+]/[SeSO32-] and complexing agents. X-ray powder diffraction and transmission electron microscopy were used to determine the phase, purity, size and morphology of the products. (C) 2002 Elsevier Science B.V. All rights reserved.