A hemodiafiltration/hemofiltration cartridge is preferably formed of a single cartridge providing multi-stage hemofiltration and hemodiafiltration defined by a first hemodiafiltration stage having first filtering elements and a second hemofiltration stage having second filtering elements. Both stages are contained in a single cartridge. The cartridge can be used in a mid-dilution scheme, a pre-dilution scheme or a post-dilution scheme.