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Introduction: In the last twenty years we can observe in modern society significant increase of fruit juices and carbonated soft drinks consumption. The most of them besides water and different additives contain citric, phosphoric and carbonic acids. The pH of these beverages is usually lower than 4.0. Frequent exposure of hard dental tissues to dietary acids leads to surface softening and irreversible erosive wear. Aim: The aim of our in vitro study was to determine the changes of enamel microhardness and elastic modulus of human extracted molars immersed into selected soft drinks (Kofola, Coca-Cola), orange juice and white yoghurt. Materials and Methods: 40 enamel samples (5x3x1.5 mm) were prepared from intact vestibular and oral surfaces of freshly extracted human molars. At the beginning of the experiment microhardness and elastic modulus were measured by nanoindentation (NanoTest NT 600, Micromaterials, Great Britain). Surface topography of enamel samples was studied by atomic force microscopy. Received data were used as control. After that the enamel samples were randomly divided into 4 groups. The samples of the 1st group were immersed to soft drink Kofola (Kofola JSC, Krnov, Czech Republic), the samples of the 2nd group to Coca-Cola (Coca-Cola HBC, Czech Republic), the samples of the 3rd group were exposed to orange juice Hello (Nivnice, Czech Republic), the samples of the 4th group to white yoghurt Klasik (OLMA, Czech Republic). The time of exposure was 5 minutes. Yoghurt and drinks had room temperature. The pH and titratable acidity of every beverage and yoghurt were determined. After immersion the samples were rinsed with distilled water and dried up. After that microhardness and elastic modulus were measured. Surface topography of the samples was studied again. Received data were statistically worked up (paired Student's t-test) and compared with initial data before exposure to acidic drinks and yoghurt. Results: The most distinguished reduction of enamel microhardness was observed among samples exposed to Coca-Cola (43.6 ± 14.4%) and orange juice (41.7 ± 3.4%). The most distinguished decrease of elastic modulus was observed among samples immersed to orange juice (15.7 ± 4.7%) and Kofola (14.9 ± 9.0%). The influence of yoghurt on enamel mechanical properties was insignificant (p > 0.05). Conclusions: The results of our experiment prooved significant reduction of enamel mechanical properties after their exposure to acidic beverages. Despite of acidic pH, yoghurt did not cause significant changes of enamel mechanical properties due to its mineral components. [ABSTRACT FROM AUTHOR]