Five dictyostelid cellualr slime molds were found in forests of Pinus densiflora and Quercus mongolica in Mt. Surak, uijeongbu, Kyunggi-do, South Korea. isolates were Polysphondylium pallidum, Dictystelium firibasis, D. crassicaule, P. tennuissimum and D. valenstemmum. Dominant soecies was P. pallidum. This species had occurred widely in South Korea as well as in the world. Especially, new dictyostelid, D. valenstemmum shim et Chang, was found in the fermentation layer of P. densiflora and Q. mongolica mixed-forest soils. D. firmibasis had not been described until now and found in the mountain forests.