Internal coating of gas and liquid pipelines can be economically justified by resulting reductions in operating costs. A typical payback period is 3-5 years. These are the primary conclusions of an economic study which used improvements in pipeline hydraulics to estimate savings in operating costs over a wide range of fluid and pipeline parameters. This is the second article (Part 1, OGJ, Feb. 29, p. 59) in a series aimed at giving pipeline operators information on protecting their pipelines.