A system for electrogenerated chemiluminescence based on the reaction of electrogenerated Ru(bpy)3(3+) with tryptophan (Trp) is described. The orange chemiluminescence was generated by reaction of Ru(bpy)3(3+) with Trp in acidic solution. The lowest detection limit was 0.1 pmol for Trp. This newly demonstrated system should prove useful for the selective and sensitive detection of Trp.