Chemistry Department, Faculty of Science, Cairo University, El-Faiyum Branch, El-Faiyum, Egypt E-mail : hamohammed@yahoo.com Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt Manuscript received 6 December 2004, revised 18 April 2005, accepted 21 June 2005 Interaction of 2-aminothiazole (AT) base with 3,5-dinitrobenzoic acid (DNB) and 3,5-dinitrosalicylic acid (DNS) gave 1 : 1 molecular species. The salts were investigated using IR, NMR and UV-Vis spectroscopic techniques. Proton transfer occurred from the acid to the hetero nitrogen atom of the aminothiazole to form a Lewis Salt. The crystal structure of AT-DNB (1) and AT-DNS (2) were determined by single crystal X-ray diffraction. Both two compounds crystallize in a monoclinic cell, (space group P21/c ). The structures were determined by direct methods and refined to R = 0.055 for 1 and R = 0.074 for 2.