Addition of clonidine to an epidural mixture of local anaesthetic and morphine improves analgesia and reduces the frequency of motor blockade during epidural analgesia. several side effects are possible mostly somnolence and hypotension. Association of continuous clonidine infusion with low concentrations of levobupivacaïne and sufentanil was not studied during labour. The objective of this study is to compare the effectiveness and the side effects of a PCEA with levobupivacaïne 0,0625 % and sufentanil 0.25 microg.ml-1, without addition of clonidine, and with addition of clonidine at a concentrations of 2 microg.ml-1.