Raman spectra for three SWNT samples doped with Br2 were studied using different excitation energies, 2.41 eV and 1.58 eV. One sample was also studied under high pressure up to 2 GPa. The vibrations in the low frequency range behave similarly for all samples. With an excitation energy of 1.58 eV, additional peaks at ca 240 cm−1 and 209 cm−1 are observed. With increasing pressure, the peak at 209 cm−1 gradually softens by 2∼3 cm−1 and becomes very weak at 1.7 GPa, while a new broader peak at ca 250 cm−1 remains constant up to 2 GPa. A number of high intensity overtone modes are observed under high pressure. These results indicate that the vibrations are attributed to bromine, not to the breathing modes of SWNTs, and that bromine resides in the bundles, possibly also inside tubes as a form of polymer.