In this study we argue that narrative storytelling and expository discussion, as 2 distinct discourse genres, differ both in linguistic expression and in their underlying principles of organization - schema-based in narratives and category-based in exposition. Innovative analyses applied to 160 personal-experience narratives and expository essays written by schoolchildren, adolescents, and adults on the shared topic of interpersonal conflict point to certain apparently contradictory facts about developing discourse abilities in the 2 genres. For example, genre differentiation is established early on (even the youngest children distinguish between the 2 types of discourse), but with age, participants tend to diverge from genre-typical content (by including expository-type generalizations in narratives and narrative-like incidents in expository texts). Also, across age groups, in local linguistic expression, participants use more advanced vocabulary and grammar in expository than in narrative texts, but in global-level discourse organization, they achieve command of expository text construction only in adolescence, whereas the principles governing narratives are established by middle childhood. We suggest that this apparent paradox can be accounted for by several interlocking factors: cognitive and linguistic development, increased experience with different varieties of discourse, and the communicative context in which a piece of discourse is produced.