The structure of (1T01) twin dislocations in Ti films evaporated on NaCl substrates at 250°C has been examined and characterized by high-resolution transmission electron microscopy. The results have revealed that a twin dislocation structure with a step height 4d(K1), where d(K1) is the spacing of the lTOl twin planes, actually dissociates into two (lTOl) twin dislocations with step heights of d(K1) and 3d(K1). The twin dislocation with a step height of3d(K1) contains an edge dislocation in the core, while that with a step height of d(K1) is a simple classical twin-dislocation structure. Twin dislocations with a step height of 2d(K1), including an edge dislocation in the core, also occur. The atomic-scale core structures of (lTOl) twin dislocations may be derived by analysis of the high-resolution images. The relative mobilities of the three types of twin dislocations are then discussed.