Recent debate on delayed ettringinte formation (DEF) as a form of internal sulfate attack -- a distress mechanism for ambient- and steam-cured concrete -- has motivated this paper, which examines relevant data from the literature and from the author's laboratory. DEF can be associated with distress in high temperature concrete, but not for ambient-curing in the absence of external SO(3) sources, or an aggregate sulfate course. The two internal SO(3) sources cited as potentially responsible -- anhydrite in clinker and high SO(3) concentrations in the silicate phases -- are shown to be absent or fundamentally innocuous.