By limiting the pipes thickness necessary to sustain high pressure, high-strength steels could prove economically relevant for transmitting large gas quantities in pipelines. Up to now, the existing hydrogen pipelines have used lower-strength steels to avoid any hydrogen embrittlement. The CATHY-GDF project, funded by the French National Agency for Research, explores the ability of an industrial X80 grade for the transmission of pressurised hydrogen gas in large diameter pipelines. This project has developed experimental facilities to test the material under hydrogen gas pressure. Then, tensile, toughness, fatigue and disc tests are performed on the base material and on the welds. Moreover, an apparatus has been designed to simulate the hydrogen gas impact on a damaged pipe section. Hydrogen gas influence has been evaluated by FEM coupling H diffusion and mechanical fields. The results stress the necessity to improve the guidelines, updating the safety margins, for high-strength hydrogen transmission pipelines.