Steam generators in the second generation nuclear power plants with pressurized water and CANDU reactors were in most cases of the shell-and-tube type. The reactor coolant passes through the tubes at the primary side and boils water on the outside of the tubes (secondary shell side) to make steam. Typical dimensions of the tubes are the diameter of about one inch or less and the tube wall thickness of about 1 mm. A few thousand tubes with shape of inverted letter U were installed in a typical steam generator. The dominant choice of material was Ni-Cr-Fe alloy Inconel 600. After some years of operation the first degradations were detected. Degradations were caused by a variety of mechanisms and were not limited to Inconel 600. A good review of designs, materials and degradation mechanisms was given in (Shah and MacDonald 1993). Replacements of steam generators solved the degradation problem mainly by the choice of different tubing material (IAEA 2008). A large number of original steam generators are still in operation and some of them may operate without replacement until the final shutdown of the plants. Consequently, the degradation of the steam generator tubes is still in the focus of research and maintenance activities. Recent examples include (Lee, Park et al. 2010), (Revankar, Wolf et al. 2009), (Hur, Choi et al. 2010), (Pagan, Duan et al. 2009) and (Pandey, Datla et al. 2009). Our main purpose is a critical compilation of the past work in the field of probabilistic assessment of steam generator degradation and maintenance strategies. The probabilistic apparatus already proposed to serve in specific cases has been consolidated and generalized to accommodate a wide range of mechanistic and empirical models describing the tube failure modes.