An apparatus for hemo(dia)filtration comprises an extracorporeal blood circuit and a supply line of a replacement fluid to the extracorporeal blood circuit. The supply line has a bifurcation which divides a main branch (24) into a pre-dilution branch (25) and a post-dilution branch (26). A pump tube tract (29) is predisposed in the supply line for coupling with a circuit pump of the replacement fluid. An expansion chamber is predisposed in the extracorporeal blood circuit and is fluidly connected to the pre-dilution branch. The invention provides a disposable fluid circuit usable for performing a hemodiafiltration treatment with pre-dilution and post-dilution which is couplable simply, rapidly, economically and reliably to a machine for monitoring the treatment.
