The fatigue limit properties of a carbon steel and a low-alloy Cr-Mo steel were investigated via fully-reversed tension-compression tests, using smooth specimens in air and in 115-MPa hydrogen gas. With respect to the Cr-Mo steel, specimens with sharp notches were also tested in order to investigate the threshold behavior of small cracks. The obtained S-N data inferred that the fatigue limit was not negatively affected by hydrogen in either of the steels. Observation of fatigue cracks in the unbroken specimens revealed that non propagating cracks can exist even in 115-MPa hydrogen gas, and that the crack growth threshold is not degraded by hydrogen. The experimental results provide justification for the fatigue limit design of components that are to be exposed to high-pressure hydrogen gas. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.