My thesis treats idioms containing the prepositions up and down . It is focused on phrasal verbs with the prepositions up and down . After giving some information about recent researches into this topic, these idioms are compared with those found in Hungarian with the equivalent prefixes fel and le . Special attention will be devoted to similarities and differences. A lot of definitions found in English idiom dictionaries and in a Hungarian dictionary are applied. My work also contins an outline of how such a comparative method works and about the different definitions found in different dictionaries. Its examples will be both English and Hungarian sentences found in the dictionaries. Idioms in general provide a wide possibility to show how rich a language is, and what nuances can be expressed with them. The difficulty of translating such items is also presented in my work, in fact in both sides of the translation. Teaching and translating idioms have been and are still a problem for teachers, but for learners as well. A perfect solution is not given here but I hope some useful ideas are found. No wonder that research in this field of linguistics will surely go on.