['Weight gain after kidney transplantation (Tx) is considered a risk factor for poor outcomes. Increased oxidative stress is associated with not only chronic renal disease and Tx, but also obesity and cardiovascular disease. The aim of this pilot study was to test whether oxidative stress is related to weight gain at 12-months after kidney Tx and to obtain preliminary insight into potential mechanisms involved.', 'Recipients (n=33) were classified into two groups; weight loss and weight gain, based on their weight changes at 12-months post-transplant. Total antioxidant capacity (TAOC) and lipid peroxidation (TBARS) were measured to evaluate oxidative stress from plasma at baseline and 12-months. A secondary data analysis was conducted to identify potential gene regulation.', 'Seventeen recipients lost (-6.63±5.52kg), and sixteen recipients gained weight (8.94±6.18kg). TAOC was significantly decreased at 12-months compared to baseline for the total group, however, there was no significant difference between groups at either time point. TBARS was higher in weight gain group, at both time points, and it was significantly higher at 12-months (p=0.012). Gene expression profiling analysis showed that 7 transcripts annotated to reactive oxygen species related genes in adipose tissue were expressed significantly lower in weight gain group at baseline, which might be a negative feedback mechanism to reduce oxidative stress.'] Is oxidative stress associated with weight gain in recipients at 12-months following kidney transplantation?