Abstract: A cannula valve arrangement made from a suitably resilient polymeric material including a body (10) having a substantially cylindrical cavity (16) for receiving a medical apparatus hub (32, 34) and a sleeve (14) having a bore (18) for receiving a cannula (28), which is open into the body cavity. A zone (20) of the body wall which defines the cavity (16) is convexly bulged from the body (10) and is adapted to snap from its convex shape into a concave shape in the body cavity (16) when pressed over-center into the body to close the bore (18) of the sleeve (14) to the cavity until again moved outwardly from the cavity (16).