We investigated mercury resistance (Hg(r)) in 52 clinical isolates of Enterococcus facealis from two different geographical regions. Eleven of the 52 strains were resistant to HgCl2, and plasmids from these enterococci hybridized with a staphylococcal mercuary resistance gene probe. Hg(r) from 5 of the 11 transferred at frequencies ranging from approximately 2 x 10-7 to 2 x 10-3.