In this study, a new type of fluorescence probe, diphenylpyrenylphosphine- conjugated alkyltriphenyl-phosphonium iodide which was accumulated in mitochondria, has been synthesized. This probe was detected peroxide in living cell. Comparison of the reactivity toward several peroxide indicated that the probe was existed in mitochondrial membrane. Using this probe, generation of peroxide in mitochondria of living cell was successfully visualized. (c) 2010 Elsevier Ltd. All rights reserved.