We report the synthesis of high purity double-wall carbon nanotubes encapsulating GdCl 3 nanowires (GdCl 3 @DWCNTs). The obtained GdCl 3 @DWCNTs were characterized by transmission electron microscopy (TEM), Raman spectroscopy, UV–Vis-NIR spectroscopy, and fluorescence spectroscopy. TEM measurements show that GdCl 3 impurities were absent on the exterior of the tubes and bundles. Furthermore, significant changes of the optical properties of the inner tubes were not triggered by being filled with GdCl 3 nanowires, which suggests that significant charge transfer does not occur between the encapsulated GdCl 3 and the inner tubes. Our results indicate that GdCl 3 @DWCNTs could be useful for various applications using the expected magnetic properties of GdCl 3 and almost unchanged optical properties of DWCNTs.[TANSO 2013 (No. 260) 279–83.]