Аннотация:The article deals with the interaction of international and native prefixes and prefixoids in Russian and Czech word-formation. We explain the reasons for interlingual asymmetry in this area: (1) the structural features of the language: e.g. In Czech language, unlike in Russian one, adverbs are easily turned into prefixes / prefixoids (rádoby-, skoro-, také-/taky-, etc.) and (2) language contacts (expressive and colloquial morphemes truc- and monstr- which were adopted in Czech from German and French and are not used in Russian). In the final part of this article we speak about processes common for both Czech and Russian languages and caused by the influence of English (by the example of new meanings of the international prefix anti-).