Statement of Problem:  Dental erosion is defined as the loss of tooth substance by chemical processes not involving bacteria. Dental erosion has been found to be a common cause of tooth wear. Clinically apparent erosion has been found to be related to dietary factors such as the acid content of the beverages.Purpose: Evaluation of enamel erosion in the primary and permanent teeth as the result of two most common acidic drinks produced in Iranian factories, Mirinda and Pepsi.Materials and Method: The outermost surfaces of 20 primary and 20 permanent teeth were polished flat by using the finest grade sandpaper and water in order to facilitate the proper measurement. The specimens were then prepared by cutting 3-4 mm of the buccal surface of teeth by diamond burs. The specimens were then rinsed with distilled water and stored in 100˚10 humidity before testing. The surface micro-hardness of each specimen was measured by micro vickers Hardness tester before, after 5 minutes, and 10 minutes exposure to fresh solution of each drink (10 teeth per test group). Mann-Whitney and Wilcoxon signed rank tests were used for the estatistical analysis.Results: The results showed that both drinks, Mirinda and Pepsi, produced significant surface hardness loss at 5 and 10 minutes of exposure time ( p =0.05). The amount of erosive effect was changed as the exposure time increased (change from 5 to 10 minutes). There was no statistically significant difference between the amounts of surface hardness loss in the primary and permanent enamel ( p >0.05).Conclusion: Both drinks may have almost similar but significant erosive effect on the primary and permanent enamel surfaces. Although there wasn’t any difference between erosive effect of the two beverages, this effect was increased with increase in time. The primary teeth enamel was not found to be more susceptibe to acidic beverage-induced erosion than the permanent teeth.Key words: Permanent teeth, Primary teeth, Erosion, Acidic beverage