The structure of a  tilt grain boundary Σ=25(710) in germanium was investigated by HREM as prepared and after sulfur segregation. The characterisation of Ge(S) system was performed using techniques such as Auger Electron Spectroscopy, Electron Energy Loss Spectroscopy and radioactive tracer analysis. Before the sulfur introduction, this grain boundary is usually sensitive to the preferential etching during the TEM sample preparation which makes the observation difficult. This effect, depending on experimental conditions, can either partially or completely disappear. The interfacial structure as prepared and after annealing under argon or under hydrogen atmosphere can be described as a stacking of several structures with different energies. After sulfur segregation no preferential etching is observed because the lowest energy structure of the as prepared grain boundary is stabilized. The tilt angle and the plane of the grain boundary remain constant.