Streptococcus faecalis strain BM6217 was resistant to high levels of all the clinically useful aminoglycoside antibiotics. This broad aminoglycoside resistance was mediated by constitutively synthesized phosphotransferase, acetyltransferase, and adenylyltransferase activities. It was inferred that phosphorylation occurred at the 3', 5", and 2"-hydroxyl groups, acetylation at the 6'-amino group, and adenylylation, probably, at the 6-hydroxyl group of the aminoglycosides. Strain BM6217 remained susceptible to the aminocyclitol spectinomycin but the combination of penicillin G with that antibiotic appeared antagonistic to this strain.