Cardiotocography is a form of fetal assessment which simultaneously records fetal heart rate, fetal movements and uterine contractions to investigate hypoxia.The objective was to assess the effects of antenatal cardiotocography on perinatal morbidity and mortality and maternal morbidity.We searched the Cochrane Pregnancy and Childbirth Group trials register and the Cochrane Controlled Trials Register (to 1 November 1998).Randomised trials comparing antenatal cardiotocography with a control group for fetal assessment.Trial quality was assessed.Four studies involving 1,588 pregnancies were included. All trials were conducted on high or intermediate risk pregnancies. Antenatal cardiotocography appeared to have no significant effect on perinatal mortality or morbidity. There was a trend to an increase in perinatal deaths in the cardiotocography group (odds ratio 2.85, 95% confidence interval 0.99 to 7.12). There was no increase in the incidence of interventions such as elective caesarean section or induction of labour. The one trial which examined an effect on antenatal patient management showed a significant reduction in hospital admissions and a reduction in inpatient stay in the cardiotocography group.There is not enough evidence to evaluate the use of antenatal cardiotocography for fetal assessment. All of the trials included in this review date from the introduction of antenatal cardiotocography and may be difficult to relate to current practice.