The authors present a retrospective study of the prevalence of thrombophilia in patients with retinal vein occlusion. The study cohort included 88 patients with central retinal vein occlusion (CRVO), 51 patients with branch retinal vein occlusion (BRVO) and 40 controls. Patients were screened for factor VIII, fibrinogen, antithrombin III, protein C, protein S, homocysteine, activated protein C (APC) resistance, ACA, factor V Leiden, prothrombin G20210A and methylenetetrahydrofolate reductase (MTHFR) C677T mutation. The most common cardiovascular risk factors were hypertension (65.8%) and prior thrombosis at any location (25%) amongst CRVO patients as well as hypertension (72.5%) and smoking (20%) amongst BRVO patients. Mean fibrinogen levels were significantly higher in all patient groups than amongst controls (CRVO: p=0.005; BRVO: p=0.004). Elevated fibrinogen levels (>4.5g/l) were significantly more frequent in the CRVO group compared to controls (p=0.037). This was not the case for the BRVO group (p=0.072). High fibrinogen levels may create hypercoagulable states by increasing blood viscosity, red blood cell aggregation, velocity of platelet aggregation and platelet reactivity. They contribute to atherosclerotic plaque growth and in vitro stabilise fibrin clots. Persistently high levels of fibrinogen might constitute an independent risk factor for RVO. However, further prospective trials to assess the potential link between elevated plasma fibrinogen and RVO have been suggested. Eight of 86 CRVO patients, three of 44 BRVO patients and none of the 39 controls were positive for ACA. Thirty of 82 CRVO patients, 23 of 43 BRVO patients and 20 of 31 controls were methylenetetrahydrofolate reductase MTHFR heterozygotes. Eleven of 82 CRVO patients, 8 of 43 BRVO patients and none of the controls were MTHFR homozygotes. There was a significantly higher rate of homozygous MTHFR mutations in the CRVO and the BRVO group, each compared to controls (CRVO: p=0.032; BRVO: p=0.011). The authors suggest elevated fibrinogen levels, ACA and the homozygous MTHFR C677T mutation as potential risk factors for CRVO / BRVO.