We present a valency lexicon for Latin verbs extracted from the Index Thomisticus Treebank, a syntactically annotated corpus of Medieval Latin texts by Thomas Aquinas. In our corpus-based approach, the lexicon reflects the empirical evidence of the source data. Verbal arguments are induced directly from annotated data. The lexicon contains 432 Latin verbs with 270 valency frames. The lexicon is useful for NLP applications and is able to support annotation. 1