In the period 1972-1978, forty peritoneal dialysis were performed in thirty seven newborn infants. Their weights were comprised between 1,250 and 5,600 gr., being under 2,000 gr. in eight cases. Peritoneal dialysis was considered as a therapeutic method integrated on the whole treatment approche applied to each critically ill newborn. Its indication was due to renal failure in twenty seven cases and to severe water and electrolyte disturbances in ten cases. Except for one newborn infant with a likely lactic acidosis, our aims in setting an adequate blood depuration and maintenacne of the water and electrolye balance were attained. In two cases we could correlate an aggravation of the clinical state with final death to complications partially due to the procedure. Other incidents in relation with peritoneal dialysis were less relevant and did not interfere with the clinical course followd by the patients. In our experience, peritoneal dialysis was a simple and highly useful method in the treatment of neonates with renal failure or severe metabolic disturbances.