Among the characteristics which set Bordeaux French apart from Standard French are the rules governing the behavior of its mid-vowels. These rules are much simpler and more extensive (in that they also apply to unstressed vowels) than in Standard French. Their application is, however, systematically conditioned by the presence or absence of word boundaries, a fact not recognized for Standard French where it has been obscured by a number of conditioning factors not operating in Bordeaux French. Another conditioning factor is the presence in the syllable following that of any mid-vowel of "e caduc," whose effect is the same whether it is elided or not. For this feature, Bordeaux French and Standard French show remarkable unity in spite of marked superficial differences. A sociolinguistic investigation reveals that the mid-vowel adjustment rules of Bordeaux French constitute an area where "standardization" is least successful, except for a few members among the high social classes. This can probably be attributed to the degree of abstraction of the process involved (standardization is more successfully achieved when a straightforward, across-the-board phonetic replacement is involved) and to the complexity of the target system (Standard French). (Author/TL)