DAF-2 diacetate is a more cell-permeable version of DAF-2, a sensitive fluorescent indicator for the detection and bioimaging of nitric oxide (NO). Upon entry into cells, DAF-2 diacetate is hydrolyzed to the less cell-permeable DAF-2 by cellular esterases, thus preventing loss of signal due to leakage of DAF-2 diacetate from cells. In the presence of oxygen, DAF-2 reacts with NO to yield the highly fluorescent triazolofluorescein. The intracellular fluorescence (generated by DAF-2 diacetate) can be readily monitored using the standard FITC filter set. DAF-2 diacetate can be utilized in cells which produce small amounts of NO, such as endothelial cells, as well as in cells which generate large amounts of NO, such as macrophages.