Higher levels of serum phosphate are independently associated with an increased risk of death in hemodialysis patients. Therefore, there has been considerable interest in controlling serum phosphate while minimizing oral calcium load. While most attention has focused on the use of non-calcium containing phosphate binders such as sevelamer and lanthanum, modifying conventional dialysis regimens to improve phosphate clearance is an alternative approach that remains relatively unstudied. A secondary analysis of a previous randomized cross-over study from our group found that the use of two dialysers in parallel resulted in a reduction in pre-dialysis serum phosphate levels. As this study was small, and the mechanisms resulting in the reduction in phosphate levels were unclear, further study is warranted. The investigators will conduct a randomized cross-over study comparing the impact of dialyzing using two dialysers in parallel with a single dialyser in hyperphosphatemic hemodialysis patients.