Accurate assessment of fluid status is a priority for patients with kidney failure undergoing long-term dialysis. There is wide variation in current volume-related practices between dialysis units and an urgent need to develop better evidence to guide practice. Clinical decisions relating to volume management are implicitly based on assessment of volume status, and there are numerous different but imperfect methods of assessment. Isotope-based dilutions are impractical for clinical use and may not be a gold standard for patients with kidney failure. Individual trends in body weight and BP have been used as a pragmatic surrogate marker for volume status. Probing the target weight based on BP is still widely practiced but may pose risks related to volume depletion and accelerated loss of residual kidney function. Clinical signs, such as elevated jugular venous pressure and leg edema, are readily accessible but have poor diagnostic accuracy and wide interobserver variability that limit their reproducibility for volume assessment in clinical trials. Lung ultrasound and bioelectrical impedance analysis have a sound scientific rationale for the assessment of extracellular volume and are appropriately associated with clinical outcomes, but neither approach has demonstrated convincingly favorable clinical outcomes in clinical trials. Other technologies for volume assessment exist but require further assessment in clinical trials. Advancements in clinical care can be made with existing technologies through comparative effectiveness trials of different fluid management strategies, routine and standardized measurement of volumetric parameters and individual patient preferences, and innovative integration of existing volume assessment methods. A systematic and globally coordinated approach to improving volume assessment and management is required to improve outcomes in patients receiving long-term dialysis.