Purpose Intravitreal somatostatin (SST) levels are decreased in patients with diabetic macular oedema. This deficit may be involved in the pathogenesis of this condition. The aim of the present study was to determine SST concentration in the vitreous fluid of patients with chronic uveitic macular oedema (CUMO) and quiescent intraocular inflammation. Methods Plasma and vitreous fluid samples were obtained during vitrectomy from 11 eyes of patients with CUMO and from 42 eyes of control subjects (idiopathic epiretinal membrane, macular hole). SST concentration was measured by radioimmunoassay. Statistics: w 2 -square test, Mann-Whitney U-test, Wilcoxon test, Spearman's rank correlation coefficient, and multivariant linear regression models. Results Plasma SST concentrations were similar in uveitic patients and controls (28.25 pg/ml (21.3-31) vs 28.7 pg/ml (22-29.5); P ¼ 0.869). A higher vitreous concentration of proteins was found in uveitic patients (1.59 ± 0.38 mg/ml vs 0.73 ± 0.32 mg/ml, Po0.0001). Vitreous SST was markedly lower in uveitic patients, both in absolute terms and after adjusting for total intravitreous protein concentration (39.37 pg/ml (6.16-172) vs 486.73 pg/ml (4.7-1833), Po0.0001; 33.1 pg/mg (3.9-215.74) vs 629.75 pg/mg (6.91-2024), Po0.0001). No correlations were found between plasma and vitreous concentration of SST in either group (r ¼ 0.191, P ¼ 0.57 and r ¼ 0.49, P ¼ 0.66). There were no correlations between vitreous SST concentration and visual acuity or macular thickness in uveitic patients (r ¼ 0.302, P ¼ 0.31 and r ¼ 0.45, P ¼ 0.13). Conclusions Intravitreous SST is decreased in patients with CUMO and quiescent intraocular inflammation. The deficit of SST may have a role in the pathogenesis of this condition.