The crystallization and phase transition of TiO2 nanotubes that are > 4 mu m in length were investigated. The nanotubes initially crystallized in the anatase and rutile phases at 300 degrees and 550 degrees C, respectively. The rutile nucleation occured initially in the nanotube-support interface. On elevating the calcination temperature above 550 degrees C, the rutile crystallites in the nanotube-support interface merged with the nanotubes and finally formed a compact rutile layer at 800 degrees C. During the anatase-to-rutile phase transition processing, a (004) preferential orientation occurred due to the regular arrangements of the nanotubes onto the titanium substrate.