Healon, a viscoelastic preparation of Sodium hyaluronate, has been reported effective in posterior segment surgery for dissection of epiretinal membranes, i.e. proliferative diabetic retinopathy and macular pucker. A more viscous substance might be more effective for this kind of surgery. Therefore, a new Sodium hyaluronate preparation Healon GV with a ten times greater viscosity at rest than Healon, was tested in an open clinical study. Twenty-four patients of both sexes and not younger than 18 years were enrolled. The follow-up time was three months. The main indications for using Healon GV were: to separate membranes from the retina, to stop bleeding and to reposition a detached retina. 0.2-0.5 ml of Healon GV was injected through a 27 gauge bent cannula and at close of surgery irrigated out of the eye. Postoperatively the patients were monitored concerning intraocular pressure, vitreous clarity, anterior chamber flare and visual acuity. Healon GV was found to make the surgical procedure simpler and safer. No inflammatory reaction and no increase of IOP was observed.