The authors evaluated the results of pars plana vitrectomy (PPV) on account of chronic uveitis in 10 eyes of nine patients. In one patient where both eyes were operated on the cause of uveitis was spondylitis ankylopoietica, in the remainder the cause of uveitis was not revealed. All eyes tolerated PPV well. PPV markedly improved the visual acuity in 7 eyes (70%), a visual acuity of 1.0-0.7 was recorded in three eyes, an acuity of 0.4-0.1 also in three eyes and an acuity of 0.04 in one eye. The cause of failure in all instances was detachment of the retina. PPV is an obvious asset in the treatment of chronic uveitis associated with thick exudation into the vitreous body.