The unconfined compressive strength of various cement-stabilized phosphogypsum mixes is described. The mixes vary in compacted dry unit weight, moisture content, cement type and content, and curing procedure and time. It is shown that the mixes behave similarly to cement-stabilized soil. The strength increases with increases in dry unit weight, cement content, and curing period. Strength decreases with increasing compaction moisture content and with a soaked curing regime. The strengths exceed a typical minimum specified unconfined compressive strength (1.7 MPa at 7 days) only at modified Proctor compacted densities (at 4% cement) and more than 14% at standard Proctor compaction level. A limited study of the effects of adding sand, hydrated lime, and calcium chloride showed that sand and small additions of calcium chloride increase the 7-day strength. Lime was ineffective. The use of constant volume molds was also shown to be effective in allowing direct control of unit weight and moisture content in compacted specimens.