The aim of the article is to sum up the most frequent lexical means used by Polish young generation to convince the addressee about the fact that the reported information is true and meant seriously as truthfulness still seems to be a highly valued featuare of our everyday verbal communication. Some 170 students were asked to answer the question What expressions do you use to emphasize your truthfulness? The author analyses the collected material and - providing that in a specific speech act on pragmatic function becomes dominant - isolates categories of assertives, directives, commissives and expressives, and oaths, gives their description and frequency.