BACKGROUND: Complications of renal failure may prevent timely evacuation of injured soldiers. Conventional renal replacement therapy is not available in forward surgical units. METHODS: Records of in-theater improvised peritoneal dialysis (IPD) in level III hospitals or forward surgical units in Iraq or Afghanistan were reviewed to determine the following: cause of renal failure and associated injuries; type of dialysate, peritoneal access, and exchange technique; and patient outcome. These data were used to propose method for IPD using commonly available materials. RESULTS: IPD is described in four patients. Abdominal or chest drains were used with either improvised dextrose-electrolyte solution or commercial dialysate. Exchanges were successful, despite fresh surgical wounds including full laparotomy, removed excess fluid and restored acid and electrolyte balance, but did not correct azotemia. Open abdominal packing prevented continuation of IPD after 48 hours. Two patients fully recovered, one died, and one patient with a poor prognosis was lost to follow-up. CONCLUSION: IPD can be delivered effectively using readily available materials in forward surgical units and level III combat support hospitals.