Abstract: A prefabricated stair system having individually pivotally mounted right angular brackets on opposed stringers, has a control bar which removably contacts the brackets to assume all brackets are arranged at the same angles with respect to the stringer so that the treads, which are supported by opposed pairs of brackets, are parallel to the floors and the risers supported by the brackets are perpendicular to the treads. The stair system is shipped as a kit and assembled in situ following a method of assembly and installation.