The efffects of freeze-thaw cycling on the static compressive strength of samples of compacted, stabilized, wet flue desulfurization (FGD) by-products are reported. The results of laboratory tests show a clear relation between higher sample water contents and decreasing strength in the freeze-thaw cycling. In the samples tested, water contents greater than or equal to 40 wt% were characteristic of all the freeze-thaw specimens exhibiting low strengths. Lime content and curing time were also identified as having a marked influence on the durability of the FGD material. Samples can maintain good strength under freeze-thaw conditions if 5 wt% lime is added before compaction and the time from compaction to first freeze is at least 60 days.