In this paper we argue that lexicalselection plays a more important role in the generation process than has commonly been assumed. To stress the importance of lexicalsemantic input to generation, we explore the distinction and treatment of generating open and closed cla~s lexical items, and suggest an additional classification of the latter into discourse-oriented and proposition-oriented items. Finally, we discuss how lexical selection is influenced by thematic ([oc~) information in the input. .
