This paper introduces an extension of distinctive-collocate analysis that takes into account grammatical structure and is specifically geared to investigating pairs of semantically similar grammatical constructions and the lexemes that occur in them. The method, referred to as 'distinctive-collexeme analysis' , identifies lexemes that exhibit a strong preference for one member of the pair as opposed to the other, and thus makes it possible to identify subtle distributional differences between the members of such a pair. The method can be applied in the context of what is sometimes referred to as 'grammatical alternation' (e.g. the dative alternation), but it can also be applied to other choices provided by the grammar (such as the two future tense constructions in English). The method has two main applications. First, it can reveal subtle differences between seemingly synonymous constructions, many of which are difficult to identify on the basis of more traditional approaches. Second, it can be used to investigate the very notion of 'alternation'; we show that many alternations are much more restricted than has hitherto been assumed, and thus confirm the claims of recent, non-derivational views of grammar.