Background: There are regional variations in causative organisms and epidemiologic patterns of corneal ulcers. It is essential to review periodically in terms of epidemiology and the microbial keratitis profiles that occur in a specific region in order to develop a comprehensive strategy for diagnosis and management of corneal ulcers. Objective: To review the epidemiology, predisposing factors, microbiological characteristics and visual outcomes in corneal ulcers at a referral center in Thailand. Methods: A retrospective review of patients with clinically diagnosed corneal ulcers presenting between January 2006 and December 2010 was performed. Results: A total of 159 patients (159 eyes) were analyzed. Ninety-one cases (57.2%) were in men. The mean age of the patients was 43.0 ± 20.0 years. The most common predisposing factor was ocular trauma found in 72 eyes (45%). Culture was grown from 123 eyes and results were positive in 52%. The most frequent causative organisms were bacteria (72%), followed by fungus (28%). The most common bacteria was Pseudomonas aeruginosa (55%) and most common fungus was Fusarium species (33%). In a comparison between fungal and bacterial groups, the latter was more likely to be associated with contact lens wear (p = 0.05). The hospitalization time for the fungal group was significantly longer than for the bacterial group (p = 0.001). The posttreatment corrected visual acuity equal to or better than 20/200 was found significantly more commonly in the bacterial group than in the fungal group (p = 0.031). While therapeutic keratoplasty was significantly higher in the fungal group than in the bacterial group (p = 0.048). Conclusion: Fungal keratitis was more severe than bacterial keratitis resulting in longer hospitalization time, poorer visual acuity, and with more chance to have therapeutic keratoplasty.