Abstract: A cuvette for use in an automatic chemical analyzer is formed of molded transparent plastic material, the cuvette having a flat box construction made of main walls, side walls and a bottom. Entrance and exit windows for a measuring light beam are formed in the side walls in such a manner the windows are recessed inwardly with respect to the side walls. A number of such cuvettes are arranged in a magazine and a plurality of such magazines are set in an automatic cuvette loader for supplying the cuvettes in a reaction line one by one. The automatic cuvette loader has a first slider for moving the magazines stocked in a container into a cuvette loading position one by one and for pushing the cuvettes in the magazine in a direction perpendicular to a discharging direction and a second slider for pushing a cuvette array in the cuvette discharging direction so as to discharge the cuvettes one by one through an outlet formed in the magazine.