We studied 37 consecutive patients, all drug addicts, who underwent 48 valve operations from 1976 through 1981. GN bacteria were the major organisms in 25 patients (64%), compared with a previous reported incidence of 10%. Operative indications were uncontrolled sepsis in 49%, embolism in 27% and heart failure in 24% of the patients. Primary operations included nine tricuspid valvectomies and 14 aortic, 10 mitral and four aortic/mitral valve replacements. Early (30-day) mortality was 2.7% (one of 37 patients); five of nine patients who had 11 reoperations survived. Long-term follow-up revealed a late mortality of 39% (11 of 28) in patients with left-sided disease; eight of the 11 patients who died had GN infection with perivalvular abscess. Thus, the subgroup with GN sepsis and left-sided disease had a combined early and late mortality of 50%, with all deaths occurring within 8 months postoperatively. We conclude that valve replacement in the presence of active sepsis can be safely performed, but GN sepsis in addicts increases the risk of early reinfection and late mortality.