A 67-year-old man with chronic keratitis was treated with a multitude of antibiotics, corticosteroids and other medicines. Despite temporary relief, perforation with iris prolapse occurred about 4 months after the initial symptoms, and the eye had to be removed. Histological examination revealed cystic bodies in the corneal stroma which could be identified as belonging to the genus Acanthamoeba. Trophozoites were seen as well. Although these amoebae are free-living organisms, occurring almost everywhere in the water and air, corneal infections are rare and have been reported only recently. It has been suggested that Acanthamoebae may only invade the tissues in the case of mixed infections or in corneas with a reduced immunological response, e.g. after corticosteroid therapy. Conservative therapy seems to have little effect, although antibiotic/antiviral/antimycotic treatment should supplement antiamoebic therapy, considering the possibility of mixed infections. Penetrating keratoplasty was indicated in most of the reported cases and usually had a beneficial effect.