Transmission electron microscopy (TEM) specimens of a first core heat of 316 stainless steel, in both the solution annealed and 20% cold worked condition, were irradiated to 46 dpa at 420°C, to 49 dpa at 520°C, and to 34 dpa at 600°C in FFTF/MOTA. Prior to irradiation, some of the specimens were pre-implanted with approximately 100 appm of helium over one-third of the specimen thickness. Microstructures and mechanical properties of these specimens were examined. Microstructural data was taken from unimplanted zones and were consistent with data in the literature for unimplanted 316 SS. Where possible, irradiation hardening of the alloys was experimentally evaluated by microhardness and shear punch. For comparison, irradiation hardening was also calculated using a barrier hardening model and the microstructural data. Experimentally measured values of yield stress were in agreement with the range of values reported in the literature regardless of helium pre-implantation and were similar to the calculated values.