A 53-year-old woman was found to have an ulcer on her successfully transplanted corneal graft. Many fungal elements were observed in the smear of the ulcerated tissue, and Alternaria alternata was cultured. The ulcer was treated with pimaricin and thimerosol topically, and 5-fluorocytocin (5FC) generally and healed to scar after two months. The ulcer did not invade the host cornea, but remained in the donner cornea in all clinical course. The MIC of five drugs on the isolated strain was following; thimerosal 0.0063, pimaricin 2.0, amphotericin B 3.2, aystatin 6.3 and 5FC 100.0 micrograms/ml each.