Quantum dots (QDs) promise to revolutionize the way fluorescence imaging is used in the cell biology field. The unique fluorescent spectral characteristics, high photostability, low photobleaching, and tight emission spectra of QDs position them above traditional dyes. We will address the ability of water-stabilized QDs to behave as effective fluorescence resonance energy transfer (FRET) donors in cells upon transferrin-receptor–(TFR) mediated endocytosis. Confocal microscopy detects whether donor QD transferrin conjugates transfer energy to acceptor organic fluorophore-transferrin conjugate molecules in endocytic compartments. QDs are shown to be effective FRET donors when internalized into cells via the transferring receptor-mediated endocytic pathway. Upon pairing with the appropriate acceptor dyes, QDs will reduce the laborious data processing that is required to compensate for bleed through contamination between organic dye donor and acceptor pair signals. The QD technology simplifies and expands the use of FRET in the analysis of complex cellular processes that may involve protein organization in intracellular membranes as well as protein-protein interactions.