The aim of this study was to evaluate the changes in body composition after glucocorticoid treatment in patients with systemic lupus erythematosus (SLE). Consecutive SLE patients were recruited for serial measurements (baseline, months 2 and 6) of bone mineral density (BMD) and body composition [bone mineral content (BMC), fat and lean mass] by dual energy X-ray absorptiometry scan after high-dose oral glucocorticoid therapy. Factors correlated with changes in body composition were evaluated. 29 SLE patients were studied (age 39.7 +/- 11.5 years; 83% women with 29% postmenopausal; SLE duration 80.1 +/- 80 months). Fourteen patients (48%) were glucocorticoid-naive. The mean maximum daily dosage of prednisolone was 32.9 +/- 6.5 mg and the cumulative prednisolone dosage in 6 months was 2.7 +/- 0.7 g. At 6 months, a significant drop in BMC of the trunk (-5.0 +/- 2.2%; P = 0.04) and whole body (-1.2 +/- 0.4%; P = 0.002) compared with baseline was observed, and so was the BMD of the hip (-1.7 +/- 0.6%; P = 0.006) and whole body (-0.7 +/- 0.3%; P = 0.01). A significant increase in the fat mass of the trunk (+14.5 +/- 4.1%; P = 0.001) and limbs (+10.0 +/- 3.2%; P = 0.004), but a non-significant drop in lean mass of the trunk (-3.3 +/- 1.8%; P = 0.08) and limbs (-0.8 +/- 2.4%; P = 0.75) also occurred. The changes in whole body BMC correlated significantly with age (rho = -0.51; P = 0.02) and changes in total fat mass (rho = 0.44; P = 0.02) but not with lean mass (rho = -0.21; P = 0.27), gender, body mass index, smoking, prednisolone dosages or changes in BMD. In SLE patients, high-dose glucocorticoids lead to an early and rapid drop in bone mass, which is more serious in older patients and correlates with an increase in body fat.