[en] The J=4→3 rotational emission line of cyanodiacetylene H-CequivalentC-CequivalentC-CequivalentN has been detected in Sgr B2. If the molecules are assumed to be in thermal equilibrium at a temperature of 30 K, a column density of 1.5 x 104 cm-2 is obtained. This observation provides further evidence that heavy polyatomic molecules exist in abundance in Sgr B2