The relationship between intrapartum fetal acid-base status and fetal heart rate (FHR) response to vibro-acoustic stimulation was investigated in 100 patients. Fetal heart rate responses were classified into three groups: acceleration of 15 or more beats per minute lasting 15 or more seconds, acceleration of ten or more beats per minute lasting 10 seconds but less than 15 beats per minute and 15 seconds, or no acceleration. The mean fetal scalp blood pH was 7.29 in both groups with acceleratory responses, and such responses were highly predictive (98–100%) of scalp pH 7.20 or above. The mean pH value for the no-acceleration group (7.22) was significantly lower than the mean pH value for both groups with an acceleratory response (P< .05), and the lack of response to the stimulus detected 90–100% of fetuses with a pH below 7.20. This sensitivity was reduced to 45% in the detection of fetuses with pH less than 7.25.