SUMMARYCellular slime molds were isolated from 75% of soil samples from 50 prairie remnants in southern Wisconsin. Total populations (cells per g of soil) were greatest in wet sites, intermediate in wet-mesic and mesic sites, and least in dry-mesic sites. Populations were slightly higher in dry than in dry-mesic sites, possibly because soils in dry sites had higher water-retaining capacities than soils in dry-mesic sites. Dominant species includedPolysphondylium violaceumin wet prairies,Dictyostelium giganteumandP. violaceumin mesic prairies, andP. pallidumandD. sphaerocephalumin dry prairies.Dictyosteliumsp. (YS) andP. pallidumboth had greater populations at the two extremes of the moisture gradient than in mesic sites. Other species isolated includedD. discoideum, D. lacteum, D. mucoroides, D. polycephalum, D. purpureumandD. rosarium.Average species diversity ranged from 3.2 species per site in dry-mesic prairies to 4.6 per site in wet-mesic prairies.