Abstract: The invention relates to a circuit arrangement for energy-saving operation of a fluorescent tube (1) whereby two respective connections (2a, 2b, 3a, 3b) are arranged on the end caps (1a, 1b) of said tube. The fluorescent tube is mechanically and electrically linked to brackets (8, 9) via said connections (2a, 2b, 3a, 3b) and can be connected to an alternating current supply (6) via a reactance coil (4) and a starter (5). The objective of the invention is to allow the fluorescent tube to be retrofitted in a simple manner. This is achieved by means of a quadrupole (4) circuit arrangement, whereby the input terminals (7a, 7b) of said quadrupole form a series connection with the two connections (2a, 2b, 3a, 3b) on one end cap (1a, 1b) and the reactance coil (4), whereby said circuit is connected in parallel to the alternating current source (6), and the output terminals (7c, 7d) of said quadrupole are electrically connected to the two connections (3a, 3b, 2a, 2b) on the other end cap (1b, 1a).