The Office of Pipeline Safety (OPS) is issuing this bulletin to owners and operators of natural gas transmission pipeline systems to advise them to review their internal corrosion monitoring programs and operations. Operators should consider factors that influence the formation of internal corrosion, including gas quality and operating parameters. Operators should give special attention to pipeline alignment features that may contribute to internal corrosion by allowing condensates to settle out of the gas stream. This action follows a review of incidents involving internal corrosion, some of which resulted in loss of life, injuries, and significant property damage. OPS’ preliminary investigation of a recent gas transmission pipeline incident found wall thinning on damaged pipe associated with the incident. The wall thinning is consistent with that caused by internal corrosion.