Abstract: An animal door assembly has a frame and a door mounted in the frame by a hinge which has a hinge axis which permits opening of the door in both directions to each side of the doorway. A spring is coupled with an edge of the door and acts between a position on the frame disposed inwardly of the door opening away from the hinge axis and a position fixed in relation to the door and offset radially from the hinge axis. The position is so arranged as to adapt the assembly to induce resilient deformation of the spring during opening of the door and to induce a reduction in the rate of deformation with movement of the door as it approaches the open position. The spring serves to urge the door towards the closed position when opened in either direction.