3 gave the 3-substituted aminopyridazines 4 . Also In addition, pyridazine-3-sulfonamides 7 were prepared from the reaction of pyridazine-3-sulfonylchloride 6 with different amines. All of these derivatives have been characterized by analytical and spectroscopic studies, and also were tested for their in vitro antibacterial and antifungal activity against a variety of microorganisms.