The present paper deals with the changes of the category of grammatical aspect during derivation of verbs from verbs in Czech. After summarizing the main issues of the long-standing debate over aspect in Czech, it is argued that formation of aspectual pairs can be seen as an integral part of derivation of Czech verbs.
In a language data resource capturing the derivational morphology of Czech, the category of aspect was employed as an important feature in modelling verb-to-verb derivation. A set of criteria used for organization of verbs in the database is presented in the paper.