Aim: To study the manifestations of progressive herpes simplex virus endotheliitis. Methods: The records of 10 eyes of 6 patients diagnosed with herpes simplex virus endotheliitis were reviewed in this retrospective case series. All patients attended the LV Prasad Eye Institute between August 1997 and May 2001. Data collection included patients' demographics, clinical details, and virological investigations. The clinical course, laboratory investigations, management, and outcome are described. Resul ts: There were 4 men and 2 women (median age, 23.5 years; range, 10 to 66 years). Four patients had bilateral involvement, 2 of whom had simultaneous onset. Best corrected visual acuity at presentation ranged from perception of hand movements to 20/50. Progressive features included bilateral severe visual loss (7 eyes), epithelial defect (5 eyes), anterior stromal infiltrate (5 eyes), and severe uveitis with hypopyon (5 eyes). Polymerase chain reaction for HSV-1 DNA was positive in 4 of 6 patients. All patients were treated with corticosteroids and acyclovir. Final visual acuity of 20/30 or better was achieved in 6 of the 10 eyes. Complications encountered were dense corneal scarring with vascularisation (4 eyes), secondary bacterial keratitis (2 eyes), and total corneal melt (1 eye). Three eyes underwent penetrating keratoplasty, with graft failure in 2 eyes. Conclusions: Clinical manif estations of herpes simplex virus endotheliitis vary from mild to severe disease. Progressive presentation includes unilateral or bilateral corneal oedema and severe uveitis with epithelial defects and stromal infiltrates mimicking bacterial keratitis. Polymerase chain reaction for herpes simplex virus may be a valuable tool for confirming viral aetiology.