Baseline data: Height (stadiometer), Weight, BMI, Height SDS, Height velocity SDS (historical past 6 months), Weight SDS, BMI SDS, Hb, BUN, nPCR, serum albumin, serum calcium, serum phosphorus, iPTH, electrolytes, high sensitivity CRP (as a marker of inflammation), dialysis adequacy (defined by single and double pool Kt/V - Kt/V is a unitless number used to quantify hemodialysis and peritoneal dialysis treatment adequacy: K - dialyzer clearance of urea, t - dialysis time, V - patient's total body water; in HD the target is 1.2), IGF-1, IGFBP-3, hip films and bone age (4,5,6,9). In addition, lean body mass/and fat mass will be assessed by DEXA (to standardize the determination of LBM, DEXA to be done mid week, after the dialysis treatment, to avoid the excess fluid commonly present after 2 days off dialysis each weekend) and quality of life will be assessed by the PedsQL 4.0 Generic Core Scales (10). The nutritional parameters that will be determined (wt/ht, ht SDS, BMI, nPCR and serum albumin) represent the currently used assessments of nutrition for these patients and have been validated as best measures of nutrition in children on dialysis (12).