OBJECTIVE To determine the role of amniocentesis in the management of severe rhesus (Rh), incompatibility. DESIGN A 10-year retrospective descriptive study. SETTING Department of Obstetrics and Gynaecology, Tygerberg Hospital, CP. STUDY POPULATION 111 pregnancies complicated by severe Rh incompatibility where management had been based on results obtained from amniocentesis. MAIN OUTCOME MEASUREMENTS Neonatal haemoglobin values, neonatal survival and short-term morbidity as compared with the position on the Liley chart after amniocentesis immediately before delivery. RESULTS Average neonatal haemoglobin value decreased for the group in the lower zone through the midzone to the upper zone, but wide scattering of individual values between the various zones occurred. Perinatal mortality rate was 93/1,000 deliveries with Rh-related deaths occurring only in the upper midzone and upper zones. One death and 7 cases of morbidity occurred after acting on misleading information from the Liley curve. CONCLUSION Amniotic fluid bilirubin values are at best an indirect evaluation of the state of disease. No serious complications are likely to occur when these values fall in the lower or lower mid-zones of the Liley chart. When bilirubin values fall in the upper midzone or upper zone, cordocentesis should be performed to prevent overreaction or to perform an intra-uterine transfusion.