OBJECTIVE We propose a nomenclature for classification of herpes simplex virus (HSV) keratitis. We hope that a more consistent classification system will lead to a better understanding of the disease processes, thus resulting in improved diagnosis, treatment, and patient outcomes. METHODS A review of the literature was performed to evaluate current HSV classification systems. These systems were evaluated in the context of both current clinical and basic science studies and our own clinical observations. RESULTS The proposed classification system is based on the anatomy and pathophysiology of the specific presentations of HSV keratitis. Anatomically, the primary level of corneal involvement, whether epithelium, stroma, or endothelium, must be elucidated. Pathophysiologically, the cause of the inflammation. whether immunologic, infectious, or neurotrophic, must be determined. There are four major categories of HSV keratitis. (1) Infectious epithelial keratitis, which is made up of cornea vesicles, dendritic ulcer, geographic ulcer, and marginal ulcer. (2) Neurotrophic keratopathy, which includes punctate epithelial erosions and neurotrophic ulcer. (3) Stromal keratitis, which is subdivided into necrotizing stromal keratitis and immune stromal keratitis. (4) Endotheliitis, which has three clinical presentations: disciform, diffuse, and linear. CONCLUSIONS We believe that by categorizing cases of HSV keratitis by their primary anatomic and pathophysiologic etiologic characteristics, clinicians can better understand and therefore treat all types of HSV keratitis. The four main categories of HSV keratitis are infectious epithelial keratitis, neurotrophic keratopathy, stromal keratitis, and endotheliitis. Each of these is subdivided to more specific clinical presentations.