High body mass constitutes a significant risk factor for morbidity and mortality in the general population, but it has been associated with an increased survival among dialysis patients. Despite reduction of weight gain with the new immunosuppressive regimes, obesity is more common in the post transplant period and its effects on adult renal transplant outcomes are controversial. The aim of our present work was to investigate the impact of pretransplant obesity and post transplant weight gain on patient and graft outcomes in childhood. In this cross sectional study sixty five consecutive renal transplant (Tx) recipients (51 boys and 24 girls) were included. Their mean age was 10.5 years and the mean follow-up was 4 years. Basal immunosuppression was steroids, cyclosporine (CsA) and mycophenolate mofetil (MMF) in all patients. At the time of transplantation mean of body mass index (BMI) was 17.2(SD: 3.2) kg/m2, namely, BMI <5th percentile in 23%; 5 to 85th percentile in 55.3% and >85th percentile in 21.7%; while at the time of our study mean BMI was 22(SD: 5.2)kg/m2, BMI <5th percentile in 8.1% and >85th percentile were 34.5%. Pretransplant obesity (BMI>85th percentile) that was more frequent in younger age (p=0.024), was associated with chronic continues decrease of GFR (p=0.01), hypertension (p=0.007), long term post Tx high weight gain (p=0.035) and pretransplant hyperlipidemia; but was not associated with gender, pre transplant hypertension, dialysis history, and acute rejection. Obesity was more common in post Tx period and it was less frequent in prolonged graft duration (p=0.01) but was not associated with acute rejection and chronic continuous decrease of GFR, hyperlipidemia, proteinuria and hypertension. In conclusion, univariate and multivariate analysis showed that pretransplant obesity had some effects on long term graft outcome; whereas post transplant weight gain was not a risk factor for graft or patient survival in our experience.