This paper gives a presentation of a corpus-based contrastive study of expressions of possibility in English and Norwegian. Norwegian and English are closely related languages and have similar linguistic resources for the expression of modal possibility, such as modal auxiliaries, adverbs, adjectives, nouns and comment clauses. The aim of the project introduced in this paper is to increase the knowledge about modal expressions on Norwegian and the differences between Norwegian and English. The paper falls into three main parts. In the first two sections hypotheses and research questions and the basis for them are outlined. The following three sections discuss some matters concerning material and method, and in the last part of the paper there is a presentation of some preliminary results of the analysis of the modal auxiliary may and its Norwegian correspondences.