Non-stress antepartum fetal cardiotocographic tracings were obtained on 2268 occasions from 1084 'at risk' pregnancies, and the findings are assessed in 834 of these that were recorded within 7 days of delivery or fetal death. The baseline fetal heart rate, reactivity, baseline variability and the response to spontaneous uterine contractions have been related to the perinatal outcome. Poor or absent reactivity, reduced baseline variability and variable or late decelerations, in response to contractions, were useful indicators of fetal compromise, but baseline heart rate was less helpful. These abnormalities can occur individually, or in combination, and the different patterns so produced have been related to perinatal outcome.