The purpose of this study was to evaluate the effects of different bases of ceramic brackets on shear bond strength and to observe failure patterns of bracket bondings. Lower bicuspid brackets whose bases designed for the macromechanical and silane treated chemical bon?ding, those for silane treated chemical bonding, those for micromechanical bonding, and those for macrome?chanical bonding were tested as experimental groups, and foil mesh-backed metal brackets as a control group. All the brackets were bonded with Mono-Lok 2^(™) on the labial surface of extracted human lower bicuspids after etching the enamel with 38% phosphoric acid solution for 60 seconds. The shear bond strengths were measured on the universal test machine after 24 hours passed in the 37°C water bath. The gathered data were evaluated and tested by ANOVA and Duncan´s multiple range test, and those results were as follows. The shear bond strengths of brackets for macromechanical and chemical bonding, those for chemical bon?ding, and those for micromechanical bonding were not different (p>0.05), but showed statistically higher than those of metal bracket and those of ceramic bracket for macromechanical bonding(p<0.05). The shear bond strengths of ceramic bracket for macromechanical bonding showed statistically lower than those of metal bracket(p<0.05). The enamel fractures and/or ceramic bracket fractures were observed in the cases of higher bond strength than that of metal bracket. These results supported that silane treated base of ceramic bracket show higher shear bond strength than that of metal bracket, and suggested that micromechanical form of ceramic bracket bases show higher shear bond strength than that of macromechanical form.