Cyclic ureas have interesting pharmacological properties that have led to their use as analogs of bioactive compounds. Several synthetic routes for urea formation by cyclization of diamines are known, based on the nucleophilic reaction of the amines with phosgene or phosgene derivatives. We have developed a procedure for a triphosgene mediated, on-resin urea cyclization. Four novel urea macrocyclic molecules were synthesized in order to demonstrate the feasibility of this method.