Standard haemodialysis is not a very efficacious treatment of chronic uraemia and patient mortality rate is still very high. The 2002 results of the HEMO study showed that alternative treatments such as 'high-efficiency haemodialysis' and 'high-flux haemodialysis' are associated with a non-significant reduction in the relative risk of mortality (4 and 8%, respectively). In an attempt to define the clinical impact of haemodiafiltration, we review some of the efficacy data from clinical studies in light of a number of factors that may be related to the high mortality among haemodialysis patients.