Demodex folliculorum has been incriminated in the development of blepharitis although much controversy persists. Certain authors suggest that Demodex is a direct pathogen in chronic palpebral conditions while others consider the saprophyte to be innocuous to skin.We conducted a prospective study of eyelashes in 100 persons, searching for Demodex folliculorum and chronic blepharitis. Microscopy in immersion oil after storage in a moist chamber was performed.The incidence of Demodex folliculorum was very high in patients with blepharitis compared with normal controls. Incidence increased with age. Harmless cuffs around the base of the eyelashes was found in 4% with Demodex irradior.Demodex should be considered as the cause of chronic blepharitis. Anti-Demodex treatment is indicated when the parasite is found.