Practical stabilization and solidification of soils and sludges exhibiting contamination from heavy metals or organic compounds can be accomplished using readily available, conventional, or byproduct cementitious (hydraulic or pozzolanic) materials, such as portland cement, slag cement, cement kiln dust, lime kiln dust, hydrated lime, and fly ash. Case histories are presented documenting the use of various combinations of cements, fly ash, and byproduct kiln dusts, since the mid-1970s to stabilize and solidify a wide range of contaminated materials. Such materials include PCB-contaminated granular road base, steel industry sludges, contaminated lake-bottom sediments, rotary kiln slag from a secondary lead smelter (acid battery reclaimer), and a very wet former fly ash fill site. Stabilization processes developed have enabled treated materials to satisfy environmental and engineering requirements. Field testing, laboratory stabilization process development, and process implementation (pilot and full-scale) are discussed.