High-resolution electron microscopy has been used to characterize the structure of ultra-thin films of titanium deposited on KBr substrate by ultra-high Vacuum (UHV) electron-gun evaporation. The size of the grains has an order of magnitude of 10 nm whatever is the substrate temperature. The observations have been carried out along the [11 (2) over bar 3] zone axis. Some of the grains contain planar defects that were identified as the twin {10 (1) over bar 1}. The atomic structure of this twin is characterized by a mirror plane similar to that observed in polycrystalline titanium; Additionally, this structure can be modified by a b(2/2) twinning dislocation.