Background:Haemodiafiltration (HDF) is a dialysis modality that combines the criteria of haemodialysis (HD) and haemofiltration (HF),so it acts by both diffusion and convection.Beta 2-microglobulin (β2-MG) is a marker of the middle molecular weight uremic toxins that it retained in patients with ESRD and its retention results in the manifestations of dialysis related amyloidosis. Objectives:To investigate the effect of on-line haemodiafiltration; by one session per week; on the serum level of β2-microglobulin and on the improvement of nerve conduction study in patients with end stage renal disease on chronic haemodialysis.Methods:A total number of 12 patients with ESRD previously on regular conventional haemodialysis for more than 4 years, were subjected to one session of haemodiafiltration (HDF) by “Gambro AK 200 ULTRA” System for 4 hours and two sessions of haemodialysis (HD) for 4 hours per week with follow up for 3 months.With measurement of URR during one HD session, URR during one HDF session, β2-MG reduction ratio during one HD session, β2-MG reduction ratio during one HDF session and follow up of serum β2-MG levels at 4 time intervals: at the start time of the treatment, after 1 month, 2 months and 3 months post HDF treatment. Also with follow up of the Nerve Conduction Study (NCS) regarding the latency, amplitude and conduction velocity for both motor and sensory responses for the median nerves in both upper limbs as well as the peroneal nerves in both lower limbs at the start of the HDF treatment and 3 months post HDF treatment. Results:URR % was significantly higher with HDF than with HD (75.6% vs. 66.9% and this difference was statistically significant (p<0.001). Reduction ratio of β2-MG level was 72.2% with HDF vs. 26.6% with HD and this difference was statistically significant (p<0.001). But the difference of β2-MG levels at the different time intervals was not statistically significant (p>0.05).The results of motor conductivity testing showed significantly higher nerve conduction velocity in post HDF treatment phase in comparison to pre HDF treatment phase in right median nerve (p<0.001) and in left peroneal nerve (p<0.001). The mean value of sensory response in amplitude as well asin nerve conduction velocity in right median nerve and left median nerve were significantly higher after HDF treatment period (p< 0.05). Conclusion:In our study, the On-line HDF had a good effect on clearance of β2-MG at the level of one session, but unfortunately at the level of follow up for three months, the serum level of β2-MG didn’t significantly changed. Also there was mild to moderate improvement of the nerve conduction study regarding motor and sensory responses after the end of this study period.