A case of photosensitivity induced by fleroxacin (FLRX) is reported. A 71-year-old man had erythema on sun-exposed areas after 5 months FLRX treatment for prostatitis. The minimal erythema dose to UVA was reduced at the initial examination and became normal 4 weeks after he stopped taking FLRX. Oral photo-challenge with FLRX 100 mg was positive, but photopatch testing was negative. Fleroxacin (FLRX), in use since 1992, is a fluoroquinolone antibacterial derived from quinoline. Photosensitivity induced by FLRX is not uncommon, but a photobiological study has not been reported. The mechanism of action of photosensitivity induced by the fluoroquinolones is considered to be phototoxic in origin in that in vitro technique studies are positive. FLRX, a quinoline derivative may be a photosensitizer as well as enoxacin, lomefloxacin and sparfloxacin.