Wurtzite CdS nanocrystals were synthesized via a hydrothermal microemulsion method. With the preaddition of increasing amounts of dodecanethiol, the resulting crystals changed from nanorods to pyramidal particles with decreasing sizes. The control effect of dodecanethiol was attributed to the competition process during the crystal growth and the relevant change in the film flexibility of inverse micelles. The Z, effects of water content, ion concentration, and hydrothermal temperature on the crystal morphologies and size distributions were also investigated. (C) 2003 Elsevier Inc. All rights reserved.