For dystoctic deliveries peridural analgesia with bupivacaine 0.25% was compared with bupivacaine 0.375%, without adrenalin. Shortening of the delivery time in cases of stagnation of dilatation, was obtained with bupivacaine 0.375%: 181 mn in the average instead of 276 mn with bupivacaine 0.25% (p = 0.05). In the case of a cervical spasm, there was release of the contraction with return of a normal dilatation leading to a shorter labour: 188 mn in the average against 340 mn (p = 0.02) with the 0.25% solution. Apgar scores were similar in both series.