The article presents failures of structures made of austenitic steels. The first part is concerned with accelerated (centrifugally) cast tubes (ϕ 52.6?×?5.8 mm) made of steel 25-35 CrNi exposed to high temperature and severe reducing environment (ac >> 1). The second part of the article presents test results related to a water meter element and a cooling water pipeline made of austenitic steel. In both cases, a relatively short period of service was accompanied by the appearance of leaks. The tests revealed that the failures were triggered by microbiological corrosion caused by a sulphur reducing bacteria and not by the welding technology applied.