·AIM: To study plasma levels of vascular endothelial growth factor (VEGF), endothelin-1(ET-1) and nitric oxide (NO) in patients with proliferative diabetic retino-pathy (PDR) before and after pan-retinal photocoagula-tion (PRP).·METHODS: In this prospective study, forty patients (23 females and 17 males, mean age 48.5±12.2) with PDR without previous PRP therapy were studied. Blood samples were obtained before and 3 months after the last PRP session. Baseline (prelaser) plasma levels of VEGF, ET-1 and NO were compared with their levels in 30 healthy age- and sex- matched controls and also with plasma levels 3 months post-PRP. ·RESULTS: Patients with PDR had significantly raised plasma VEGF (375±89ng/L), ET-1(20±5ng/L) and NO (135±53μmol/L) when compared with healthy control group (P<0.01). After PRP, there was a significant re-duction in plasma VEGF (179±66ng/L), ET-1 (11±5ng/L) and NO (91±49μmol/L) levels at 3 months' follow-up but still significantly higher than healthy controls.·CONCLUSION: Patients with PDR demonstrate elevated VEGF, ET-1 and NO, which decreased after successful laser treatment.