Objective. Weight gain is a side effect of glucocorticoid (GC) use, but the natural history and health implications of changes in weight that occur during the treatment of inflammatory disease are not understood. Methods. We evaluated data from the Wegener's Granulomatosis Etanercept Trial. Patients were categorized according to clinical outcome at 1 year: remission (no disease flares), single flare, or multiple flares. Risk factors for gaining ≥10 kg were examined in multivariate models. Results. Weights at baseline and 1 year were available for 157 (93%) of the 168 patients analyzed. During year 1, the mean cumulative prednisone dosage in the multiple flares subgroup was 7.9 gm, compared with 6.0 gm and 3.9 gm in the single flare and remission subgroups, respectively (P < 0.001). Patients in these subgroups gained an average of 2.6 kg, 4.1 kg, and 5.8 kg, respectively (P = 0.005). Weight gain did not correlate with cumulative GC dose (R = 0.10, P = 0.25). Thirty-five patients (22.3%) gained and maintained ≥10 kg in the first year. New diagnosis of Wegener's granulomatosis at baseline was an independent predictor of gaining ≥10 kg at 1 year (odds ratio 19.7, 95% confidence interval 2.4-162.6, P = 0.006). Among the 78 patients in the remission subgroup, 40 sustained remissions through the 2-year time point. For these 40 patients, the mean weight gained at year 1 did not regress by the end of year 2, despite the absence of continued GC use. Conclusion. Disease control was associated with lower cumulative GC doses but greater weight gain. More than one-fifth of patients gained >10 kg in the first year of treatment. The quantity of weight gained by patients during treatment has potential future health implications. © 2008, American College of Rheumatology.