Betaines of bicyclic imidazo-thiazoles were synthesized by the reaction of clectrophiles such as methyl isocyanate, methyl isothiocyanate, allyl isothiocyanate and ketene with 3-methyl and 3-phenyl-5, 6-dihydroimidazo [2,1-b] thiazole. In this reaction, the methyl group which was substituted at 3-position increased the yields of the products in comparison with those from phenyl group substituted substrates. Also, the betaines reacted with methyl iodide to give imidazo-thiazolium salts which were unstable at high temperature and converted the quaternary ammonium salts of original biheterocycles.