PURPOSE: To compare the characteristics of ocular herpes simplex virus (HSV) in patients with and without atopy. DESIGN: Retrospective cohort comparative study. METHODS: Patients who presented at the Cornea Service, Wills Eye Hospital, between March 2003 and March 2004 who had been previously diagnosed in the same institution as having ocular HSV diagnosis or were just diagnosed as having the disease were asked to complete a study questionnaire that enabled categorization into atopic and nonatopic. In April 2005, 223 patients who agreed to be in the study had their charts reviewed, and 125 patients were excluded according to exclusion criteria: immunosuppression, follow-up less than one year, previous history of penetrating keratoplasty (PK) out of the Cornea Service, and no active HSV episode during follow-up. MAIN OUTCOME MEASURES: Incidence of all types of HSV recurrences. SECONDARY OUTCOME MEASURES: Bilaterality, visual loss, need for PK , and secondary bacterial infection in both groups. HSV episodes were classified into infectious, inflammatory, and mixed for analysis. RESULTS: Ninety eight patients (110 eyes) were included in the study. Atopic/nonatopic (P value): the mean follow-up was 11.6 (+/- 10.6)/8.8 years (+/- 8.4) (P = .14); the mean incidence of HSV episodes per year of follow-up was: total episodes 0.32 (+/- 0.36)/0.28 (+/- 0.33) (P = .14), infectious 0.16 (+/- 0.22)/0.10 (+/- 0.14) (P < .01), inflammatory 0.11 (+/- 0.19)/0.11 (+/- 0.19) (P < .01), and mixed 0.09 (+/- 0.20)/0.07 (+/- 0.16) (P = .06); bilateral HSV was present in 9/3 patients (P = .22); the mean loss of vision was four lines of Snellen in both groups; PK was performed in 14 of 16 eyes (P = .45); secondary bacterial infection was present in two of four eyes (P = .26). CONCLUSIONS: Atopic patients had considerably more infectious and fewer inflammatory episodes when compared with nonatopics.