Abstract. Intermittent lumbar epidural block, using lidocaine without (series I), or with epinephrine (series II), for pain relief in labour was carried out in a total of 190 women with uncomplicated pregnancies. In a number of randomly selected cases in these two series the uterine contractility, the foetal heart rate pattern, and the acid-base balance of the mothers and their foetuses were studied. Transitory decrease in uterine activity, primarily due to depressed intensity of the contractions, was observed after each injection in both series. This phenomenon was, however, much more pronounced in cases where epinephrine was added to the local anaesthetic solution. In both series the effect on the contractions declined with the number of injections. Ominous foetal heart rate patterns were rare and occurred almost exclusively in association with transient maternal hypotension. Good correlation was found between maternal arterial, and arterialized capillary blood with respect to the acid-base components. The acid-base values in foetal scalp blood, maternal capillary blood, and in umbilical cord blood showed a less pronounced tendency to metabolic acidosis in cases where epidural blocks were given than in cases in a non-anaesthetized control group. Prolongation of the second stage was accompanied by the development of metabolic acidosis in anaesthetized, as well as in non-anaesthetized cases. In the epidural series, however, this acidosis tended to appear later and to develop more slowly, indicating an overall good and stable intrauterine foetal condition.