This paper addresses the question of how English and Spanish encode the modal meanings of possibility and necessity. English modals and Spanish modal periphrases emerge as ‘cross-linguistic equivalents’ in this area. Data from two monolingual ‘comparable’ corpora — the Bank of English and CREA — reveal (i) differences in grammatical conceptualization in the English and the Spanish traditions and (ii) the relative inadequacy of classifications of modality for a translation-oriented contrast in this area. An English-Spanish contrastive map of the semantics (and expressive means) of modality will be an effective way to make relevant and accurate cross-linguistic information available. It is also the first step towards identifying potential translation pitfalls.