PDT is an established cancer treatment modality, This can be attri buted to the attractive basic concept of PDT; the combination 0 1' two therapeutic agents , a photosensiti zing drug and light, which are relatively harmless by themselves but combined ultimately cause more 0 1' less selective tumor destruction, The bacteri ochlorophyll - derivatived photosensitizer s are known to be s tabl e and highly effïcient, ln thí s study, we conducted a seríes of experiments to develope the light induced anticancer drugs against oral cancer cell , We tested the cytotoxi city of the hydroxybacteriochlorine by MTT assay and observed the cell death pattern(apoptosis or necrosis) after PDT by hoechst 33342 and propidium iodide s taining methods, lC50 value of the hydroxybac teriochlorine was 3 1 ， 3 ng/ n띠， At higher doses of hydroxybacteriochlori ne () 60ng/ rnQ) , cancer cells died exclus ively by necrosis after PDT By contrast, at lC50 value, hydroxybacteri ochlorine induced cancer cell to undergo apop totic c e ll death, The induct ion begins approximately 6 hours a fter PDT, We inves tigates intrace l1 ular localization of hydroxybacte riochlorine by oral cancel‘ cell via confocal laser scanning mi croscopy, Oral cancer cells dua l-stained with hydrox ybacteriochlo1' ine and organelle-specific flu orescence probes (Mi totracker , Lysotracke1', ER- Tracker) revealed an intracellular f1 uores c ence dis tribution restricted to cyt oplasmic compartments with no det ectable fluorescence in the nucleus, Confocal im ages of cells containing hydroxybacte1'iochl orine were never overla p to mitochondria, lysosome . endoplasmic reticulum when digita lly overla pped with tqe organel1e-specific f1 uorescence p1'obe images o{' the same cells These results demons trated tha t the hydroxybacte1' iochlorine may have a fun ction as a photosensitizer and cytotoxicity hydroxy bacteriochlo1'ine for o1'al cancer cell is more sensitive than head & neck cancer cell 0 1' ce1'vical cancer cell Therefore PDT using hydroxybacte1'iochl orine is suita ble treatment for oral cavity carcinoma patients