Polycrystalline nanorods of CdS were successfully prepared by a novel solvothermal method using simple initial materials of sulfur and Cd(Ac)2.2H2O in pyridine at 160 degrees C. TEM, HRTEM and SAED analyses reveal that the polycrystalline nanorods with the lengths from 400 to 1000 nm and a mean diameter of ca 40 nm are assembled with highly oriented quantum dots of face-centered cubic CdS. The chemical reactions under the current solvothermal conditions involve the first reduction of sulfur by acetate anions to S2-, and subsequently the formation of intermediate complex CdS(Py)0.5 with nanorod-like morphology, as well as finally prolonged solvothermal process to the formation of the polycrystalline nanorods. Therefore, a new intermediate-sacrificed mechanism to direct the formation of cubic CdS polycrystalline nanorods was proposed.