The invention provides novel formulations of guanylate cyclase-C("GCC")agonist peptides and methods for theiruse in the treatment of gastrointestinal diseases and disorders, includinggastrointestinal cancer. The GCC agonist formulations ofthe invention can be administered either alone or in combination with one ormore additional therapeutic agents, preferably aninhibitor of cGMP-dependent phosphodiesterase or a laxative.