Glutathione-capped CdTe quantum dots (QDs) are successfully synthesized in aqueous solution. Their fluorescence emissions are tunable between 500 and 650 nm. The as-prepared QDs have a quantum yield (QY) of up to 45% (see figure), which is comparable to or better than most QDs prepared by using an orgianometallic route. The glutathionecapped CdTe QDs are successfully conjugated with bioprobes for cell-imaging applications.