As long as the illicit use of heroin and other drugs continues in our society, infective endocarditis will remain a significant medical problem in the drug-using population. The majority of infections are produced by S. aureus, and the tricuspid valve is most commonly involved. Addicts, unlike the general population, may also develop endocarditis with a variety of gram-negative bacilli and have a higher incidence of fungal infection. The outcome of each individual infection is dependent on the prompt recognition of the underlying valvular infection and the institution of antimicrobial therapy. Infection of the tricuspid valve has a much more favorable prognosis than does infection of the aortic or mitral valves. Fungal endocarditis, and frequently gram-negative bacillary endocarditis, require valvular surgery to effect a cure.