In Rhesus incompatibility, prenatal RhD typing of the fetus requires intrauterine blood sampling by cordocentesis or by chorionic villus biopsy. Amniocentesis is easier to perform, and carries a lower risk of enhancement of maternal immunization. Therefore, we evaluated polymerase chain reaction (PCR) for fetal RhD typing in amniocytes which were isolated from amniotic fluid (18-40 gw) obtained by amniocentesis (n=26) or during delivery (n=27). In the clinically most important group of children from RhD-negative women (n=25) and in 28 newborns of RhD- positive mothers, we found a 100 percent agreement between the findings of PCR and the results of serologic typing. If these encouraging results are confirmed in a larger series, the method could be used for the clinical management of RhD-negative women with Rhesus incompatibility and a heterozygous RhD-positive partner.