We describe the synthesis of water-soluble PEGylated semiconductor nanocrystals and the characterization of their optical properties and colloidal stability by fluorescence and UV spectrometers. The fluorescence intensity of PEGylated CdSe/ZnS in PBS buffer was observed to be 75% of the initial values of conventional CdSe/ZnS in chloroform. The PEGylated CdSe/ZnS exhibited higher fluorescence intensity than PEGylated CdSe and CdSe/CdS in PBS buffer. The colloidal stability of PEGylated QDs in PBS buffer was estimated by transmittance as a function of time at 37 degreesC. The PEGylated CdSe/ZnS showed a colloidal stable dispersion in PBS buffer during 24 h.