Two factors prompted the research which led to the writing of this article: first, the apparent general consensus amongst linguists both inside and outside Spain that the phonology of Old Castilian is monolithic in terms of geographic and sodal space, and that it has more or less stagnated in the mould of traditional grammars, and, secondly, the insistence of many linguists on seeing some aspects of contemporary Spanish phonology as characteristic of certain non-standard varieties of Spanish, wilhout investigating whether the same features might not also be found in Old Castile.