Corneal biopsy can be an effective aid in establishing diagnoses in a variety of infections, dystrophic and degenerative conditions, corneal manifestations of systemic diseases, and drug-induced changes. Preoperative planning and proper preparation of the tissue are stressed. In a series of 87 cases, the indications for biopsy were ulcerative keratitis in 42 cases, nonulcerative lesions in 25 cases, dystrophic and degenerative processes in 15 cases, and corneal manifestations of systemic diseases in 5 cases. Of the 42 cases of ulcerative keratitis, the presence of bacteria, fungi, and Acanthamoeba organisms was excluded in 33 instances (79%). Organisms observed in 9 (21%) of the 42 ulcerative cases included 4 with bacteria, 3 with fungi, and 1 each with Acanthamoeba organisms and virus.