This paper takes up the issue of theme category analysis of trade talk, understood as a verbal interaction between a customer and a sales representative. This category is a matter of essential importance, as it is one of key generic determinants of trade talk. Moreover, this paper covers the problem of thematic structure description in dynamic discourse, which represents a considerable part of talk, rather than single utterance. Therefore, in the aspect of topic category, trade talk analysis requires such form of description that allows to establish global topics, repetitive during any trade talk and independent neither of the branch nor the item or service being sold.