Denting is a form of damage that results from the rapid, linear growth of magnetite on carbon steel tube support plates in tube-to-support plate crevices. The pressure of the corrosion products distorts the tubes as well as the support plates. Although denting was first thought to be confined to those recirculating steam generators that had been converted from phosphate to AVT, it has now also been observed in plants still on phosphate, as well as in some that started on AVT. In some units, slightly abnormal eddy current signals have been observed at the top of tube sheets. No denting has been observed so far in the B and W once-through steam generators. In all, some 14 plants are affected. Inconel 600 tube defects and leaks were first observed at Surry and Turkey Point, which were severely dented. The cracks originated from the primary side, and were found to be caused by primary side stress corrosion cracking of highly strained tubing. Some minor leaks have subsequently occurred in a few other steam generators. Suggestions are included of work to elucidate the quantitative aspects of stress corrosion cracking.