This master's thesis deals with biaspectual verbs in Russian and Czech language. The theoretical part is divided into two main chapters. The first one provides short overview of main areas of aspectological research. Individual subchapters explain and describe basic aspectological concepts - aspect, aspectual pair, aktionsart etc, their functional features and mechanisms of creating aspectual pairs. The second theoretical chapter is devoted to the phenomenon of biaspectuality. It presents different approaches to the nature of biaspectuality and issues of classification of biaspectual verbs. It also maps statistical data about biaspectual verbs in Russian and Czech and describes dynamics of their development. The practical part represents a contrastive analysis of 50 Russian and 50 Czech biaspectual verbs. Main goal was to explore functioning of biaspectual verbs in Russian and Czech, find their new potential aspectual partners, examine mechanisms of their creating and determine extent of their semantic overlap with original borrowed biaspectual verbs, using selected electronic corpuses, the internet and own examples. Finally, based on results of the analysis, are formulated main tendencies of the development of biaspectual verbs in Russian and Czech. Key words Aktionsart, aspect, aspectology,...