Bromination of 1-hydroxyimidazole 3-oxide and 1-hydroxy-2-methylimidazole 3-oxide using bromine in acetic acid gave 2-bromo-1,3-dihydroxyimidazole hydrobromide and 4,5-dibromo-1,3-dihydroxy- 2-methylimidazole hydrobromide, respectively. In contrast, bromination in aqueous mixture (acetic acid, methanol, dimethylformamide, tetrahydrofuran) yielded 2,4,5-tribromo-1-hydroxyimidazole. Crystal structures of four compounds were determined by X-ray diffraction.