A series of Fe-Cr-35Ni alloys was irradiated to doses ranging from 12 to 36 dpa with fast neutrons at 375–600°C and to 59–117 dpa at 675°C with Ni⁺ ions. The primary purpose of this study was to examine the effect of silicon and titanium on both microstructural evolution and the tendency of Fe-Cr-35Ni alloys to spinodally decompose during irradiation. As expected, the addition of these solutes suppresses void swelling and alters the microstructural evolution. They do not appear, however, to suppress the tendency toward spinodal-like decomposition, but only to change somewhat the microstructural consequences of the decomposition.