Infection is a major cause of morbidity and mortality in systemic lupus erythematosus (SLE). A review of all SLE admissions to our hospital during a 5-year period was conducted to determine the rate and nature of infection, and its association with overall disease activity, measured by the SLE Disease Activity Index (SLEDAI). Eighty-one patients (79 women, 2 men) were admitted for a total of 2,738 days (176 admissions). There were 53 proven infections, giving an infection rate of 1.94/100 hospital days. Twenty-three (43.4%) of these were major infections (requiring IV antibiotics). Two of 3 deaths were due to septicemia. By logistic regression analysis, infection was significantly associated with disease activity (p = 0.005), but not with disease duration or prednisone dosage. Our data confirm that infection is common in hospitalized patients with SLE, is associated with overall disease activity independent of prednisone dose, and causes significant mortality. These facts should be borne in mind when hospitalization is considered for patients with SLE.