This paper describes the building of a valency lexicon of Arabic verbs using a morphologically and syntactically annotated corpus, the Prague Arabic Dependency Treebank, as its primary source. We present the theoretical account on valency developed within the Functional Generative Description theory. We apply the framework to Arabic and discuss various valency-related phenomena with respect to examples from the corpus. We then outline the methodology and the linguistic and technical resources used in the building of the lexicon. Valency lexicons can find application in automatic parsing as well as in language generation. 1.