Alendronate is a new bisphosphonate, primarily used for the treatment of osteoporosis and several other bone diseases. Herein we report a case of a patient showing an acute retinal pigment epithelitis (ARPE) following oral administration of alendronate due to osteoprosis. A 50-year old female referred to our observation complaining visual blurring and metamorphopsia in her left eye. She did not report ocular impairment in the past. Her clinical history was unremarkable for any systemic disease except she had being suffering for osteoporis for 6 months treated by means administration of oral alendronate. Her visual acuity was 20/40 OS and 20/20 OD respectively. There was no vitritis or anterior uveitis. At fundus examination subtle clumps of hyperpigmentation surrounded by a paler halo of hypopigmentation around macula of the retinal pigment epithelium (RPE) were shown in OS. In the right eye ophthalmoscopy showed some cluster of irregular pigmentation above the fovea associated with slight hypopigmentation surrounding the clump. Fluorescein angiography (FA) revealed an irregular patchy area of early hypofluorescence, surrounded by hyperfluorescence, while fading in the late phase ( Figure 1A). Earlyphase and midphase indocyanine green angiography (ICG) showed a patchy macular hypofluorescence in both eyes (Figures 1B and 1C). Similar disseminated spots of hypofluorescence were shown at the periphery nasally to the optic disk; hypofluorescent halo with a petaloid like appearance of the macular area was observed in OS on late ICG. Patient discontinued treatment with alendronate. She underwent weekly ocular examination up to 4 weeks. Her symptoms improved in OS with VA of 20/20 in 1 week after discontinuation. FA and ICG revealed some patched areas of irregular hypofluorescence surrounding the old spots due to filling defect of choroidal vessels and characterized by late staining of dye on FA and no leakage (Figures 2A and 2B). Hypofluorescent areas were shown on both intermediate and late ICG phases with reducing size compared to the acute phases in the same areas.Acute retinal pigment epithelitis (ARPE), also known as Krill's disease, is characterized by an acute and severe loss of vision in young, healthy adults with a self-limiting course and affecting both males and females equally [1]. It is thought to represent areas of RPE inflammation with breakdown of the pigment epithelial barrier and subsequent leakage of serous fluid. We report a case of a patient in which ARPE occurred after a long term administration of oral alendronate. These side effects are solved with discontinuation of therapy. A number of medications encompassing various forms of administration, including topical formulations, periocular and intraocular injections, and systemic medications, have been associated with uveitis. Bisphosphonates are primarily used to treat osteoporosis [2]. They are generally well tolerated, even though several medications in this class have been associated with uveitis or other ocular side effects [3]. Bisphosphona...