[en] Creep and corrosion tests in simulated HTR helium were conducted at FIAT laboratories on thirteen commercial casts of Grade 2 (solution annealed) Alloy 800. Compositions are shown in Table 1. Some results from five casts tested earlier at CIIR, Oslo are also included in the report. Gas compositions are summarised in Table 2. Analysis of creep curves (Figs. 1, 3, 5, 6, 9 and 11) and isochronous stress-strain data (Figs. 2, 4, 7 and 10) has enabled estimates of creep strength to be made for the alloys under test (Table 3) and these agreed quite well with manufacturers typical data at 700 and 750°C (Fig. 23). At 650°C most of the alloys had lower creep strengths than manufacturers data would suggest, partly because many of the alloys for this programme were deliberately chosen for their relatively low titanium and aluminium contents. Rupture data at 650°C agreed well with that from other sources (Fig. 24). At 800°C, the alloys were generally weaker than manufacturers data would have suggested. This was particularly noticeable when the helium tests were conducted under carburising conditions (Figs. 2 and 19). At no temperature was Alloy 800H consistently stronger than the material supplied to the older Grade 2 specification.