Sixteen species of cellular slime molds were isolated from Southeast Asian forest soils. Ten of these,Dictyostelium mucoroidesBrefeld,D. purpureumOlive,D. polycephalumRaper,D. lacteumvan Tieghem,D. rhizopodiumRaper and Fennell,D. lavandulumRaper and Fennell,D. vinaceo‐fuscumRaper and Fennell,D. coeruleo‐stipesRaper and Fennell,Polysphondylium violaceumBrefeld, andP. pallidumOlive have been previously described and are well‐recognized species occurring in other parts of the world. Two, one in the genusDictyosteliumand one belonging to the family Guttulinaceae, are considered species by the author but have not been formally described. Four are described in this paper as new:Dictyostelium intermedium, D. multi‐stipes, D. bifurcatum, andAcytostelium subglobosum.A new varietypapilloideumofD. lacteumis also described. One other discovery of special interest is an isolate ofPolysphondylium violaceumwhich produces abundant macrocysts, now known to be the sexual stage in the life cycle of cellular slime molds.