A sprayer for liquids (10) is disclosed with a trigger pump comprising a body (11) which can be applied to the mouth of a container and a liquid delivery nozzle, a pumping chamber (22) being formed in the body (11) which is in communication with the inside of the container and the delivery nozzle (16), through a one-way suction and delivery valve (30), a USD (Upside Down) device being provided rearward of said pumping chamber which allows operation of the sprayer in the upright and upside down position, consisting in a cylindrical chamber (40) closed at the top with a stopper (27) and having at its bottom a hole (44) in communication with said pumping chamber (22), shut off in the Up position by a ball (42) which, in the Down position, frees said hole (44) and slots (47) formed in the wall (46) of the chamber (40), putting the inside of the container into communication with the pumping chamber (42) through said slots (47) and said hole (44), said cylindrical chamber being slanted backwards so as to allow the operation of the sprayer also in horizontal position.