PURPOSE: To report an eye with corneal endotheliitis and increased intraocular pressure in which the trabeculum demonstrated immunoreactivity for herpes simplex virus. METHOD: Case report. A 62-year-old man presented with increased intraocular pressure, keratic precipitates, and corneal stromal edema in his left eye. The tissue excised during trabeculectomy was immunohistochemically examined for herpetic viruses. RESULT: Immunoreactivity for herpes simplex virus was identified in the trabeculum. CONCLUSION: Herpes simplex virus may cause trabeculitis and increased intraocular pressure in patients with corneal endotheliitis, (Am J Ophthalmol 1999;127:721-722, (C) 1999 by Elsevier Science Inc. All rights reserved.).