The aim of this study was to evaluate the in vitro effects of exposure to acidic beverages on microhardness of enamel and dentin. Thirty enamel specimens and thirty dentin specimens were obtained from extracted bovine maxillay incisiors. Enamel and dentin specimens were divided into three groups and treated with acidic beverages as follows; Group 1 : cola(pH 2.52), Group 2 : plain soda water(pH 2.93) and Group 3 : orange juice(pH 3.75). Erosive treatment was performed by storing each specimens for 5 min in 50ml solution of cola, soda water and orange juice. Average microhardness values(VHN) were determined before and after erosive treatment. All beverages produced significant loss of microhardness of enamel and dentin. Microhardness of enamel was reduced in the following order: Group 1 : $42.71{pm}4.36(%)$, Group 2 : $37.09{pm}6.25(%)$, Group 3 : $35.46{pm}4.98(%)$. Microhardness of dentin was reduced in the following order: Group 1 : $17.14{pm}3.42(%)$, Group 2 : $13.89{pm}3.18(%)$, Group 3 : $13.82{pm}3.50(%)$. The differences between group 1 and group 2, 3 were statistically significant(p< 0.05).