Technical Abstract: The inheritance of the ability of winter wheat plants to survive two kinds of freezing stress was investigated in a five-parent diallel cross. Plants were acclimated at +4°C for 5 wks and frozen with or without a –3°C, 16-hour pre-freezing (PF) period prior to freezing to damaging temperatures. The PF treatment resulted in significantly increased survival of plants when frozen to the same test temperatures as the NPF tests. When test temperatures were adjusted such that the overall mean survivals of the populations were the same under the two pre-freezing treatment conditions (-10 to -12°C with NPF; -14.5 to -16.5°C with PF), 276 progeny lines survived the NPF and PF treatments equally well, 40 progeny lines survived the PF treatment more frequently, and 52 progeny lines survived the PF treatment significantly less often. Lines that survived the PF tests as well or better than the NPF tests apparently developed significantly more freezing tolerance during the pre-freezing treatment and tolerated the lower test temperatures of the PF tests, while the 52 lines that survived the PF tests less frequently were unresponsive to the PF treatment. Diallel analysis indicated most variation was due to additive genetic effects, but nonadditive effects were significant in two of the 20 crosses. It may be possible to combine additive and nonadditive effects to develop cultivars that are exceptionally tolerant of freezing episodes with or without an extended pre-freezing period.