The natural history of the cardiovascular manifestations of systemic lupus erythematosus (SLE) have been altered by corticosteroids which exert their own cardiovascular effects. This study describes clinical and necropsy observations in 36 corticosteroid-treated patients with SLE and compares them to necropsy observations in patients with SLE reported before the use of corticosteroid therapy. The 36 patients averaged 32 years of age, and 33 were women. Systemic hypertension was present in 25 (69 per cent) and left ventricular hypertrophy in 23 (64 per cent) patients. Hypertension was twice as common in the 19 patients who received this drug for more than 12 months (average 38 months) than in the 17 patients who received this drug for less than 12 months (average 6 months), and was almost five times more common among our patients than in patients with SLE in the presteroid era. Congestive cardiac failure occurred in 15 patients (43 per cent), eight times more frequent than that reported in noncorticosteroid-treated patients with SLE. Subepicardial and myocardial fat was increased in all 36 patients. Lupus carditis was similar in frequency but differed morphologically in our patients compared to those not treated with corticosteroids. Libman-Sacks-type endocardial lesions, present in 18 (50 per cent) of our patients, were smaller, fewer in number, univalvular rather than multivalvular, and mainly left-sided. Most verrucae were either partly or completely healed, and some were calcified. Pericarditis, present in 19 (53 per cent) patients, was predominantly of the fibrous type. Myocarditis was present in three patients, each of whom also had endocarditis and pericarditis. The lumen of at least one of the three major coronary arteries was narrowed more than 50 per cent by atherosclerotic plaques in 42 per cent of the 18 patients who received corticosteroids for more than 1 year, but in none of the 17 patients who received corticosteroids for less than 1 year. Four of the eight patients with narrowed coronary arteries had myocardial infarcts. Although vital to the management of SLE, corticosteroids have an over-all deleterious effect on the heart. Systemic hypertension and left ventricular hypertrophy appear or, when present, worsen; congestive cardiac failure increases; epicardial apartment of Me