The incidence of infective endocarditis in drug addicts is increasing with the spreading of intravenous drug abuse. The tricuspid valve is the most commonly involved valve followed by the mitral valve. We evaluated prospectively 22 patients with a mean age of 23 years, presenting with addiction-associated endocarditis endocarditis and referred to our institution during a three-year period. The tricuspid valve was involved in 13 instances, mitral valve in 4, mitral plus tricuspid valve in 5 patients and aortic valve in 1 case. Staphylococcus aureus was the most frequent infective organism (15x), followed by Streptococci (4x), Corynebacteria (2x) and one case with a mixed infection. Six patients were positive for an HIV-infection and 17 had evidence for a chronic viral hepatitis. Ten patients (3 of them HIV-seropositive) were treated surgically. Resection of the tricuspid valve with (1x) or without replacement (4x), resection of vegetations and valve repair (2x), mitral valve replacement (2x), aortic valve replacement (1x) were performed. In case of tricuspid endocarditis, the decision whether to proceed with resection, repair or replacement with a bioprosthesis was taken according to valve pathology and the psycho-social situation of the patient. When the vegetations involved only one leaflet and could be removed easily, vegetectomy with annuloplasty or with repair using autologous pericardium was performed. Valvulectomy without replacement was the chosen method for those where persistent or recurrent drug abuse could not be excluded. A bioprosthesis was inserted when the tricuspid valve was completely destroyed and there was a proven abstinence from drugs over a period of several weeks preoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)