This work scrutinises, evaluates and systematises the modern exchange rate theories. Its aim is to familiarise the reader with the concepts of expectation, Purchasing Power Parity and Interest Rate Parity, which together form the basis of the following analysis of monetary and portfolio theories of the exchange rate determination. Then, it provides a comparison of the various approaches to these theoretical frameworks with regard to their respective authors. The paper is concluded by an evaluative description of the conditions under which such theories could be applied.