Chalcopyrite-type CuIn(SXSe1-X)(2) solid solution with 0 <= X <= 1 was successfully prepared by using mechanochemical process (MCP). The MCP is a process which causes physical and/or chemical change by mechanical energies, such as pulverization, friction and compression. The phase in the obtained powder was analyzed by X-ray diffraction, and the microstructure was observed in an scanning electron microscope (SEM). The optimum rotational speed for the MCP increases and the mixing period decreases with increasing the sulfur content in the Culn(S,Se)(2) (CISS) solid solution. For the preparation of CuInSe2, the optimum rotational speed was 250 rpm, and the milling period was 30 min, and, for CuInS2, the optimum rotational speed is 500 rpm, and the mixing time is 15 min. We do not recognize the difference in the particle size distribution of the CISS solid solution. The smallest particle size is about 0.2-0.3 mu m, the largest size is 7-10 mu m, and the average size is about 2-3 mu m. (c) 2004 Elsevier B.V. All rights reserved.