Homocysteine is considered as independent predictor of cardiovascular risk. Patients treated with haemodialysis (HD) exhibit elevated homocysteine levels, even four times higher than the general population does. This study focuses on the determination of the vascular risk in patients treated with conventional HD and haemodiafiltration on-line (HDF). It was also considered important to determine whether there was a relationship between homocysteine and the variables given to the patient such as dialysis dose, obesity and treatment with folic acid, vitamin B6 and vitamin B12. A one-year cross-sectional observational study was conducted on patients initially treated with renal replacement therapy such as HDF on-line and conventional HD. Data collected included patient's age, sex, aetiology, duration of dialysis treatment and association with dialysis session, including data on body mass index, waist circumference, treatment with vitamin B6, B12 and folic acid. The results obtained conclusively indicate that patients treated with renal replacement therapy such as HDF on-line exhibit lower homocysteine levels than those treated with conventional HD. Therefore we can conclude that: homocysteine markers indicate that patients treated with HDF on-line are exposed to lower average vascular risk.