There are evidences describing that the prices of prescription medicines can affect users, suppliers, and, in particular, payers in the health care system. Despite the significant effects of prices, the information regarding their characteristics is scarce. The objective of this study was to examine the prices and price variations of prescription medicines in an actual setting. A cross-sectional study on the prices of prescription medicines listed in a hospital formulary was undertaken. The medicines (n=1531) listed in the formulary were recorded according to the category of the medicine (essential or non-essential medicines), manufacturer types (local or foreign), dosage forms, therapeutic classifications (classes), and prices per unit in Baht. This study used coefficients of relative variations (CRVs) to determine the extent of price variations. Results revealed that the mean prices of non-essential and foreign medicines were significantly greater than those of its counterparts by 1.7 and 21.2 times, respectively. On an average, the classes with the highest prices were blood-related, antineoplastic, and endocrinological agents, while those with the lowest prices were the psychotherapeutic, CNS, and cardiovascular agents. The majority of the medicines (37%) were in the price range of >10-100 Baht. The price variations of different classes of medicines varied from about 100% to 600%. The mean price and CRV levels (low and high) formed four groups of medicines with different risks of high prices and variations to payers. In conclusion, the prices are associated with the category and manufacturer type. The prices and their variations could be used to distinguish the classes of medicines that possess different risks of high prices and variations to payers. Identifying the classes with high prices and high variations, high prices and low variations, and low prices and high variations is necessary for careful intervention to reduce the effect of prices and their variations on payers.