During the course of experiments on the transformation of lignans to phytoestrogenic substances, such as enterodiol (END) and enterolactone (ENL), a previously isolated bacterium, Eubacterium (E.) sp. strain SDG-2, capable of phenolic p-dehydroxylation in the biotransformation of secoisolariciresinol diglucoside to END and ENL, was concluded to be Eggerthella (Eg.) lenta (Eg. sp. SDG-2) on the basis of 16S rRNA gene sequence analysis. The bacterium could transform (+)-dihydroxyenterodiol (DHEND, 3a) to (+)-END (1a), but not for (−)-DHEND (3b) to (−)-END (1b) under anaerobic conditions. By incubation of a mixture of (+)- and (−)-dihydroxyenterolactone (DHENL, 4a and 4b) with Eg. sp. SDG-2, only (−)-DHENL (4b) was converted to (−)-ENL (2b), selectively. On the other hand, we isolated a different bacterium, strain ARC-1, capable of dehydroxylating (−)-DHEND (3b) to (−)-END (1b) from human feces. Strain ARC-1 could transform not only (−)-DHEND (3b) to (−)-END (1b), but also (+)-DHENL (4a) to (+)-ENL (2b). However, the bacterium could not transform (+)-DHEND (3a) and (−)-DHENL (4b). Both bacterial strains demonstrated different enantioselective dehydroxylation.