Abstract: A blood aerator comprises an aerating vessel having a vessel body provided with ports for a gas- and liquid-tight connection to a blood hose and at least one gas hose. A simplified and reliable handling is permitted in that a port for the blood hose and a port for a lower gas hose are separately provided on the bottom portion of the vessel body, the port for the lower gas hose contains a hydrophobic filter element, which is impermeable to blood and permeable to gas, and the port for a second gas hose is provided on the top portion of the vessel body.