We screened 183 different clinical anaerobic and aerobic bacteria isolated from humans and other animals for the presence of the ermF gene using a polymerase chain reaction (PCR) assay. The ermF gene was detected in 107 (58%) clinical isolates, including 42 (61%) of 69 gram-positive bacteria and 65 (57%) of 114 gram-negative bacteria. Twenty-five ATCC isolates were also tested; 20 (80%) carried the ermF gene. The gene products from the ermF PCR from four isolates were sequenced and showed 95-99% nucleotide homology with the ermF gene and 98-99% amino acid homology with the gene product. Eleven (58%) of the 19 gram-negative donors tested were able to transfer the ermF gene. All nine (100%) of the gram-positive donors tested transferred the ermF gene, using either Enterococcus faecalis or Haemophilus influenzae as the recipients.