We have reported a case of high-level gentamicin-resistant enterococcal endocarditis as a complication of intravenous narcotic abuse. Because routine screening of enterococcal blood isolates for high-level aminoglycoside resistance was not done, the patient possibly received suboptimal therapy. This case amplifies the necessity of a systematic screening program for enterococcal blood isolates to detect high-level resistance to gentamicin and streptomycin in clinical laboratories.