The aqueous synthesis of thiol-stabilized semiconductor CdTe colloidal nanocrystals has been revisited. We found optimal conditions for the synthesis of high-quality CdTe NCs through a study of the influence of the initial conditions (structure and concentration of Cd-thiol complexes) on the quality of the CdTe nanocrystals. A numerical calculation shows a clear correlation between the concentration of CdL (where L is (SCH2COO)(2-)) in the initial solution and the photoluminescence quantum efficiency of the CdTe nanocrystals.