Objective. Although patients with systemic lupus erythematosus (SLE) have an increased risk of coronary artery disease (CAD) compared with persons without SLE, the burden of CAD among SLE patients is unknown. This study was undertaken to estimate this burden.Methods. We used the Nationwide Inpatient Sample of the Healthcare Cost and Utilization Project to estimate the number of hospitalizations for CAD among patients with SLE in the US in 1998. CAD diagnoses included acute myocardial infarction (MI), unstable angina, cardiac catheterization, percutaneous transluminal coronary angioplasty, or coronary artery bypass grafting as the primary reason for hospitalization. We compared these estimates with the frequency of hospitalization for other reasons.Results. There were an estimated 98,217 hospitalizations among patients with SLE in 1998. Of these, 11,947 (12%) were among men, 43,674 (44%) were among women <50 years of age, and 42,596 (43%) were among women >50 years of age. There were 4,951 hospitalizations for CAD, with 1,763 of these for acute MI. In women <50 years old, there were an estimated 311 hospitalizations for MI. Hospitalizations for CAD were less common than hospitalizations for SLE itself or for infections, and in young women, were less common than hospitalizations for complications of chronic renal failure.Conclusion. CAD is an important comorbid condition in patients with SLE, but is not as common a reason for hospitalization as SLE itself, infections, and, in some patient subgroups, chronic renal failure.Premature morbidity from coronary artery disease (CAD) among young women with systemic lupus erythematosus (SLE) has been demonstrated in several observational studies (1-4). Manzi and colleagues reported that the relative risk of acute myocardial infarction (MI) in young women with SLE was 52 times higher than in women without SLE (2). In a study by Esdaile and colleagues (4) and in a previous study by one of us (3), the risk of acute MI was increased ϳ8-fold in patients with SLE. While these studies demonstrate a markedly increased relative risk of CAD in patients with SLE, they do not provide information on the burden of CAD in these patients. Moreover, these studies raise the question of how morbidity from CAD compares with morbidity from other causes in SLE. This information would help us understand the relative impact of CAD on the health of SLE patients and help prioritize allocation of limited health care resources.Since most patients with suspected acute coronary syndromes are hospitalized, hospitalizations for CAD can be used as one measure of disease burden. We determined the number of hospitalizations for CAD in 1998 in a national population-based sample of patients with SLE and examined how often CAD was the principal reason for hospitalization, relative to other causes of morbidity.