Summary The course of uremic syndrome can be accelerated in bilaterally nephrectomized dogs treated with peritoneal lavage solution containing either 1% urea or 0.015% potassium isocyanate. It is suggested that ammonium isocyanate formed from urea in aqueous solutions may contribute to the uremic syndrome via carbamylation reactions with free amino acids and proteins. Blood ammonia levels were not significantly elevated in any of the animals tested.