A retrospective study of 391 severe infectious keratitis admitted to King Chulalongkorn Memorial Hospital from January 1988 to December 2000 were analyzed. Most patients came from the central part of Thailand. There were 2 bimodal peak incidence distributions which fell in the age group 21-30 and 51-60 years of age. The most common predisposing to corneal ulceration was trauma from several materials, including leaves, branches, dust and stone, which accounted for 47.82 per cent. Culture results were collected 74.68 per cent (292/391). The data showed negative culture results of 52.74 per cent (154/292), positive results occurred in 47.26 per cent (138/292); including bacteria 32.53 per cent (95/292), fungus 11.64 per cent (34/292), virus 2.05 per cent (6/292) and mixed organism 1.02 per cent (3/292). Pseudomonas aeruginosa was the most common bacteria isolated; 47 per cent. The second most common was Streptococcus pneumoniae which accounted for 9 per cent. Fusarium spp was the most common fungus found (34.29%); Aspergillus and Curvularia spp were the next (20.0% each). Herpes simplex was the most common virus isolated; 83.3 per cent. The treatment of infectious keratitis included application of topical/intraocular injection of antimicrobial agent and surgery, which accounted for 184 cases. Penetrating keratoplasty was the most common surgery performed, 34.24 per cent (63/184), followed by evisceration and enucleation accounted for 25 per cent (46/184).