Abstract: An elongated luminaire is provided having at least one fluorescent lamp and a louver arranged therebelow. The louver consists of lamp-parallel longitudinal reflectors and reflecting cross-oriented lamellae arranged transversely thereto and subsequently of V-shape in cross section. The lamella legs have a parabolic shape in cross section. A light guiding plate is provided extending from one leg of each cross-oriented lamella, extending diagonally upwardly towards and almost adjacent to the lamp. Each light guiding plate substantially overlaps the interspace between neighboring cross-oriented lamella in the vertical projection. Thus, the entire light flux, emerging downwards, is directed, depending on the position of the cross-oriented lamellae and of the light guiding plates, in the desired direction into the lower hemisphere so that it is possible to obtain different light distribution curves of symmetrical or asymmetrical shape with characteristic preferred directions.