Dislocations in (101¯2), (112¯2) and (112¯1) twin interfaces in hexagonal-close-packed metals are investigated using computer simulation techniques. The geometrical aspects of these defects, i.e. their Burgers vectors, b, and step heights, h, are obtained using a recently developed treatment of interfacial defects which takes into account the total symmetry of the crystals. It is shown that, in addition to the twinning dislocations identified by previous treatments based on the symmetry of the crystals' lattices, two further types can arise, in principle, if the symmetry of the particular interfacial structure in question is appropriate. Several dislocations with different b and h have been modelled for the three boundaries considered in order to assess their possible significance in deformation processes. It is found that classical twinning dislocations having combinations of relatively small |b|and h have smaller line energies in (101¯2) and (112¯1) interfaces than is the case for the (112¯2) twin. However, the core structures, in particular the core widths, are very sensitive to the interatomic potential used and can be extremely wide, especially for the (101¯2) and (112¯1) boundaries. In the case of the (112¯1) interface it is found that classical twinning defects with Burgers vector b and step height h decompose into other defects, predicted by the crystallographic theory, with parameters b and in this case. These defects can lead to twinning in such a way that all atoms are sheared into the correct positions without the need for shuffing. A further type of dislocation decomposition is reported in the case of (112¯2) interfaces, but these dislocations do not lead to twinning.