This case study describes a structural integrity assessment of a 220 kV overhead power line. The line comprises 70 pylons over a distance of approximately 30 km, predominantly in a valley location. The pylons are spaced at intervals of approximately 400 m and each pylon is approximately 32 m in height. The line was originally constructed in the 1950’s, approximately 50 years prior to the requested structural integrity assessment. This paper describes the independent assessment that was carried out. The review established site-specific safety factors at the time of original design and construction; at the time of the review (2007), accounting for the possible presence of the “Thomasstahl” steel; and in the future, at the anticipated end of pylon life (in 2012).