We conducted a retrospective study to characterize the clinical course, microbiologic spectrum, and risk factors for endocarditis and for associated mortality in a large series of patients with documented pacemaker endocarditis. Using a computerized search through the medical records of 10 major hospitals in Israel from 1982 to 1992, and carefully reviewing the charts, we identified 44 patients with pacemaker endocarditis. The cases were categorized as definite (n = 25), probable (n = 12), or possible (n = 7) infective endocarditis based on strict case definition. Fever and chills were the most common symptoms. Increased ESR, leukocytosis, microscopic hematuria, and anemia were the most common laboratory findings. A relatively high proportion of the patients were diabetic. The most common source of endocarditis was infection acquired by the placement procedure or infection of the pacemaker pouch. Demographic, clinical, and laboratory features were similar to those of endocarditis patients of a similar age range without pacemakers, although the frequency of fever and chills was higher in our patients than in those patients and splenomegaly, vascular embolic phenomena, and new or changing murmurs were rare in our patients. The major pathogens were Staphylococcus aureus and Staphylococcus epidermidis, similar to other series of pacemaker-associated bacteremia and similar to the microbiologic findings of early prosthetic-valve endocarditis. However, this microbiologic profile is different from that of native-valve endocarditis. Although the present series did not show a statistically significant advantage to electrode removal over conservative treatment, when analyzed together with pooled data from other studies, it suggests that the surgical approach is preferable.(ABSTRACT TRUNCATED AT 250 WORDS)