Aim There are changes in blood flow during the clinical stages of diabetic retinopathy with increasing leukostasis and secondary elaboration of cytokines. This study evaluated the vitreous concentrations of haemodynamicrelated (endothelin-1 (ET-1) and nitric oxide (NO)), inflammatory and anti-inflammatory (interleukin-1 receptor antagonist, IL-1 Ra) cytokines in the diabetic patients (with nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR)), compared them with those of control patients (full thickness macular hole, FTMH) and correlated to macular structural indices. Method Vitreous samples from five FTMH patients representing normal controls were analysed together with the vitreous samples of 15 patients with NPDR and five with PDR. The vitreous concentrations of nitrite (total NO), ET-1, and prostacyclin was determined using ELISA kits (R&D Systems, Minneapolis, MN, USA) according to the manufacturer's instructions. A sandwich luminescent immunoassay technique was used to determine IL-1b and IL-1 Ra concentrations. Results In the different clinical groups, there were no differences in the vitreous NO and prostacyclin concentrations. In NPDR, the median ET-1 concentration (0.7 pg/ml SD 70.8 pg/ml) was significantly reduced (Po0.05), compared to PDR (6.35 pg/ml SD 70.6 pg/ml) and FTMH (3.6 pg/ml SD 70.14 pg/ml). Its concentration also positively correlated with foveal thickness and macular volume (Po0.05) in patients with NPDR and macular oedema. IL-1 b was detected in PDR, and diabetic patients demonstrated a lower concentration of the anti-inflammatory cytokine IL-1 Ra.Conclusion Reduced concentrations of ET-1 in NPDR may reflect the haemodynamic changes of NPDR. The IL-1 Ra concentration suggests a change in the anti-inflammatory environment of the diabetic retina.