Trailer for treatment of four-legged animals, comprising: - a floor (12) and a frame (14) which bounds an animal set-up space with passage opening, the frame being provided with a barrier which is movable between an open position and a closed position - a wheel suspension connecting at least two wheels with the frame - a tow bar (30) which is movable sideways relative to the frame and the floor between a central position, in which the tow bar in a longitudinal median plane projects forwards with respect to the frame and the floor, and a side position, in which at least a front part of the tow bar (30a), with respect to the position of the tow bar in the central position, is moved sideways for clearing an area in front of the passage opening (18).