Abstract: This thesis deals with one of the most crucial fields of E U social policy, namely with the principle of non-discrimination at work. The purpose of the thesis is to describe and analyze antidiscrimination legal regulations, specifically at work. The issue is dealt with both in the context of international and national law. It also enables to get an idea of the way of transposition of obligations of the Czech Republic resulting from the E U membership, including possible implications stemming from improper transposition. Special attention in this respect was paid to the general antidiscrimination act and problems preceding its adoption including its judicial review by the Constitutional Court of the Czech Republic. The concepts relating to equality and discrimination, in particular the principles of equal treatment and non-discrimination are central to E U law. They belong to the so-called horizontal issues. After the entry into force of the Lisbon Treaty, social policy still falls within the so-called shared competence between the E U and member states. Discrimination at work still is quite a common problem, just its forms changed. It often occurs in its covert form, which means its proving is despite of various measures, such as burden of proof transfer, rather problematic. Formally harmonized regulation of prohibition of discrimination should in any case be followed by effective exercising of the forementioned principles in practice, since the primary objective of harmonization is to properly implement the principle in day-to-day reality.