BACKGROUND Pars plana vitrectomy has both diagnostic and therapeutic potential in chronic uveitis. In this paper the therapeutic value of vitrectomy is investigated. METHODS This is a retrospective study on 25 eyes that underwent pars plana vitrectomy with therapeutic intent. Surgery was considered in patients with severe vitreous clouding or macular pucker and in those who responded poorly or not at all to conventional treatment for uveitis. The mean period of follow up was 4.5 years, varying from 2 to 12 years. RESULTS Improved vision was observed in 56% of the eyes (14/25). Twenty-four percent of the eyes (6/25) had stable vision. Macular edema disappeared in 40% (10/25) of cases and persisted in 60% (15/25). Two of the nine eyes with persistent macular oedema progressed to a macular hole. Four of the six eyes with macular pucker suffered recurrence, one ended in phythisis, while the pucker was cured in only one patient. Twelve percent of the eyes (3/25) subsequently experienced a recrudescence of uveitis, making systemic treatment necessary. One patient presented, after vitrectomy, a traction retinal detachment with proliferating vitreoretinopathy. No complications or recurrences were seen in 44% of the eyes (11/25). CONCLUSIONS Vitrectomy has a definite place in the treatment of chronic uveitis, both on the functional level, with improvement or stabilisation of visual acuity and on the therapeutic level, with possible reduction or cessation of systemic treatment.