This paper describes a large-scale language-independent evaluation of the use of Thematic Hierarchies in natural language generation. We translate from a corpus of sentences reflecting the full variety of behavior of Levin-based verb classes. The corpus is used as input to a generation system that utilizes the same thematic hierarchy for realizing relative argument surface positions in two languages: English and Spanish. The output was manually evaluated by English and Spanish speakers. The contributions of this work include: (1) an improved thematic hierarchy over an earlier implementation; (2) a large-scale evaluation of the use of thematic hierarchies in two languages; (3) an implementation of a language independent module for natural language generation; and (4) the creation of a single tool for incremental development of multilingual lexicons. Cross-referenced as UMIACS-TR-2001-59