PURPOSE: Posterior sub-Tenon's steroid injections (PSTSI) are a standard drug delivery method used for the treatment of chronic uveitis of the posterior segment. The aim of this study was to analyse the indications, efficacy and complications of PSTSI in the treatment of chronic uveitis. METHODS: During the period 1990-1994, 53 (9.5%) of 558 patients (58 eyes) followed up in the uveitis clinic received a total of 162 PSTSI of triamcinolone acetonide 40 mg in the superior quadrants. Indications for treatment were vision inferior or equal to 0.7 and/or intolerable visual disturbance. Only patients in whom PSTSI were the only treatment parameter changed were analysed. Among the main parameters analysed were visual acuity, aqueous laser flare photometry, intraocular pressure (IOP) and complications. RESULTS: Anatomical location of uveitis was as follows: anterior HLA-B27-related uveitis with CME (1 patient/1 eye), intermediate uveitis (28/32), posterior uveitis (10/10) and panuveitis (14/15). Mean duration of follow-up was 448+/-57 days. Visual acuity improved significantly from 0.40+/-0.03 to 0.79+/-0.07, with 59.4% of eyes having a gain of 2-5 Snellen lines and 18.7% a gain of >5 lines. Mean aqueous flare photometry decreased significantly from 29.6+/-3.5 to 13.6+/-2.2 photons/ms. Mean IOP increased significantly from 13.6+/-0.5 to 18.5+/-0.8 mm Hg with a rise of pressure >8 mm Hg in 23 cases (36%), transient in 16 cases, but chronic in 6 cases, needing filtering surgery. Partial superior ptosis was seen in two cases and cataract progressed in seven cases. CONCLUSION: PSTSI are very effective in restoring visual acuity in chronic uveitis of the posterior segment, without systemic complications, but at the expense of intraocular hypertension, a complication that was found more frequently than expected.