Peritoneal dialysis (PD) is widely used in chronic and acute disorders, Acute hydrothorax (AH) is a complication of PD that contraindicates further use of the method. Two cases are reported herein. One patient was a 13-year-old girl with endstage renal failure due to steroid-resistant nephrotic syndrome, Three days after initiation of PD (4 x 1250 ml/day), she developed cough and dyspnea due to right-sided hydrothorax. Chemical analysis showed that the fluid in the pleural cavity was peritoneal fluid, The hydrothorax persisted despite dialysate volume reduction, Because construction of an arteriovenous fistula was not feasible (because of thrombotic complications), talc poudrage of the pleural cavity was performed. Pleuroscopy failed to locate the communication through the diaphragm, PD was resumed after ten days with no further complications, The other patient was a six-year-old boy with acute renal failure due to hemolytic uremic syndrome. Forty-eight hours after the beginning of PD (12 cycles/24 hours, 30 ml/kg), a positive fluid balance and impaired breathing suggested right-sided hydrothorax. This diagnosis was confirmed by findings from a physical evaluation and plain chest film. PD was stopped and intermittent hemodialysis via a Quinton intracaval catheter was initiated. The outcome was favorable. Hydrothorax is an infrequent complication of PD that should be looked for when respiratory symptoms develop after PD initiation or when the fluid balance is positive. Continuation of PD can lead to respiratory distress. In most cases, the hydrothorax persists despite a decrease in dialysis volume or temporary discontinuation of PD, requiring use of another dialysis method. Pleural poudrage can be performed in the few cases where no alternative to PD is available.