Some Authors found changes in plasma aminoacids concentration in patients with chronic renal failure treated with conservative therapy or with dialysis. Particularly they observed a reduction in the concentration of essential aminoacids (EAA) and an increase of the non essential (NEAA), with increase in their ratio. In our study we analyzed the plasma aminoacids pools in 12 children with chronic renal failure treated with hemodialysis. We have measured the plasma aminoacids concentrations before and after hemodialysis to evaluate their variations and their role in the pathogenesis of some symptoms of uremia. A decreased concentration of EAA and an increased concentration of NEAA, before hemodialysis, were observed. These findings were not modified by this therapy, but turned out to be related to protein intake.