Abstract: A blood chamber for an extracorporeal blood circuit comprises a blood inlet port (2), a blood containment chamber (3), a first conduit (8) which connects the blood inlet port (2) with the blood containment chamber (3) and which has an end tract (8a) that terminates in the blood containment chamber (3) with a horizontal inlet component. The first conduit (8) comprises a pre-terminal tract (8b) which precedes the end tract (8a) and which has at least a second horizontal component which is directed in an opposite direction to the horizontal inlet component. The blood chamber is used in an arterial line of a dialysis set for guaranteeing a regular and gentle blood flow.