The efficacy of natamycin (pimaricin) was studied and compared with the standard amphotericin B, using a reproducible model of keratomycosis from Candida albicans in the rabbit. C. albicans DSM 70010 (2.5 X 10(5) cells) was injected into the corneal stroma of both eyes. All eyes developed a corneal ulcer without pretreatment with immunosuppressive agents. Forty-eight hours after inoculation, the animals were divided into five groups: I (10 eyes) and II (12 eyes) receiving natamycin drops, 1%; groups III (12 eyes) and IV (12 eyes) receiving natamycin, 2.5%; the control group (14 eyes) receiving 0.9% NaCl. For better penetration of the drug, the epithelium of groups I and III was removed every 3rd day. Half of the control group was debrided as well. In a further series, the penetration of natamycin into the cornea and aqueous humor was studied. There was no difference between the treated eyes and the control eyes concerning complications (descemetocele or perforation). It is concluded that natamycin (pimaricin) is inferior to amphotericin B and not effective in controlling experimental keratomycosis.