Three FHR deceleration areas of fixed durations related to the onset of the concomitant uterine contraction were evaluated automatically with a small digital computer during labor. The correlations between these areas and the fetal scalp blood pH values were studied. The deceleration occurring 80 to 140 seconds after the onset of each uterine contraction during the 20 minutes preceding the fetal blood sampling presented the best correlation (r equals minus 0.453) with fetal pH values. In addition to FHR deceleration area, baseline FHR variability should be considered in predicting fetal condition.