Intrapartum fetal scalp blood lactate was measured by a simple, rapid method. Its potential as an indicator of fetal oxygenation was assessed in comparison with blood gas and pH measurements. The normal ranges for lactate values in fetal scalp and cord blood were derived. Asphyxiated babies were found to have significantly higher lactate levels in fetal scalp blood taken close to delivery, and also in cord blood, than did healthy babies at birth. Suspicious and ominous intrapartum continuous fetal heart rate patterns were associated with higher lactate levels than was the normal baseline fetal heart rate with no decelerations. Poor fetal condition at birth and abnormal fetal heart rate patterns were also clearly associated with low fetal scalp blood pH values, but were poorly associated with abnormal blood gases and derived acid base values. In babies with normal fetal heart rate patterns, the presence or absence of meconium in the amniotic fluid was not related to the fetal scalp or cord blood lactate levels, nor to the distribution of Apgar scores, provided the babies' airways were cleared immediately at birth. The specificity and sensitivity of fetal scalp blood lactate measurement as a predictor of neonatal asphyxia were as good as those of pH measurement or continuous electronic fetal heart rate monitoring. The method of lactate assay used in this study is simple and easy to learn, and the instrument is robust, reliable and suitable for clinical use by different operators.