The objective of this study is to review the literature and an empirical research on the costs and adequate levels of international reserves for Brazil in the period 1999-2016. The costs of maintaining international reserves will be estimated in three modes: i) sterilization; ii) opportunities; and iii) social costs. The adequate levels of reserves are estimated by four types of approaches present in the literature: 1) traditional metrics; 2) combination of rules; 3) scenario analysis and 4) optimization model. The results show that levels of international reserves are above adequate levels by precautionary approaches, probably because the accumulation has also occurred due to mercantilist reasons, and the excess of international reserves may lead the country to excessive costs for its maintenance. Sterilization costs were lower than those found by Pellisser (2016) due to the exchange variation of the period from 2002 to 2016. We have contributed to the literature by consolidating the costs of sterilizing the reserves for a longer period of time than those previously consolidated by Gollo and Triches (2013), we estimate for the first time the social and opportunity costs of international reserves for Brazil, we calculate the appropriate levels of international reserves by the classic approach of 20% of M2, the combination of 100% of the short-term external debt minus the current account and by the Tiwari scenario analysis (2013a) that had not been calculated for Brazil, and extended the time period calculated by Vonbun (2013) of reserves by the model of Jeanne and Racière (2011) for Brazil by extending the period from 2012 to 2016.