The article explores the relationship between functionalism, loyalty and fidelity in specialized translation. In a first step, it discusses the basic principles of functionalism in translation, the first of which (the translation purpose determines the translation method) gives rise to a debate on the ethical aspects of functionalism. To make the functionality concept applicable to translator training and translation practice, the author has introduced the complementary principle of loyalty, which, unlike faithfulness, or fidelity, refers to a trustful and fair relationship between the persons interacting in a translation process. In the process of loyally producing a functional translation, the translator may rely on intertextual relationships between the texts in both the source and the target culture.