In order to understand the mechanism for the size and shape control of colloidal cadmium chalcogenide nanocrystals, CdE (E = S and Se) nanocrystals with various size and shapes were synthesized. As-prepared CdE nanocrystals obtained without further size-sorting process were observed with transmission electron microscopy (TEM) and X-ray diffraction (XRD) and were found to be nearly monodisperse and highly crystalline with the quantum size diameters below 10 nm. In the present presentation, the effects of process variables including monomer concentration, reaction time, and initial molar ratio of Cd to E precursor, on nucleation and growth of nanocrystals are discussed.