The tribological characteristics of polytetrafluoroethylene (PTFE) sliding against austenitic stainless steel was evaluated under dry condition by using a pin-on-disk wear tester coupled with an environmental test chamber, and effects of gaseous hydrogen were examined. Results indicated that the wear behavior of unfilled PTFE was affected by the counterface roughness, the chemical composition of the stainless steel and also the type of gaseous environment within the test chamber. Especially, the specific wear rate of PTFE slid against 316L stainless steel became significantly smaller in the hydrogen environment compared with that in dry air and argon. Microscopic observation revealed that the formation of the PTFE transfer film on the stainless steel surface was enhanced in the hydrogen environment. The dense PTFE film formed in hydrogen had a preferable lubricating property and might be effective to reduce the PTFE wear amount in the sliding surface.