The English possessive's (POSS-S) is widely regarded as a clitic which attaches at the right edge of noun phrases. The so-called "group genitive", where POSS-S attaches after a postmodifier (the man in the corner's hat), is crucial to theoretical accounts. We evaluate both theoretical and descriptive treatments. We then describe the actual use of POSS-S in the spoken component of the British National Corpus, with particular attention to postmodified possessors, demonstrating that the crucial pattern is surprisingly marginal and that at least one other pattern has been missed entirely. This leads to discussions of grammaticality versus usage, of postmodification, and of the factors that condition the use of poss-s and their relevance to theory. © John Benjamins Publishing Company.