One area of linguistics which has developed very rapidly in the last 25 years is phraseology. Corpus study has shown that routine phraseology is pervasive in language use, and various models of recurrent word-combinations have been proposed. This paper discusses aspects of frequent phraseology in English: the distribution of recurrent multi-word sequences in different text-types and the structure, lexis and function of some frequent multi-word sequences. Most of the data come from a major interactive data-base which provides extensive quantitative information on recurrent phraseology in the British National Corpus (BNC). This data-base, available at http://pie.usna.edu, has been developed by William Fletcher. Quantitative phraseological data have important implications for linguistic theory, because they show how findings from phraseology can be related to independent findings from other areas of linguistics, including recent studies of grammar and of semantic change. However, the very large amount of data itself poses methodological and interpretative puzzles.