The overcoating of CdS:Mn nanocrystats by a thin shell of non-doped US or ZnS results in remarkably improved photoluminescence properties. The CdS:Mn/CdS and CdS:Mn/ZnS nanocrystals presented in this work (see figure) show a much more efficient Mn-related photoluminescence than the non-coated nanocrystals. These nanocrystals are expected to find applications in flat-panel displays,. high-density optical data storage materials, and fluorescence labels for biological imaging.