Prenatal karyotype analysis was performed on cultured fetal cells obtained by transabdominal amniocentesis at the 15th and 20th week of pregnancy in 63 high risk pregnancies. The reason was advanced maternal age in 42 cases, a previous child with a chromosome anomaly in 13 cases, and parental balanced chromosome translocation in 7 cases. One mother was a haemophilia A carrier. Two mothers over 40 were found to be carrying a 21-trisomic fetus. In the group of parental balanced translocation one fetus showed an unbalanced translocation karyotype, two were karyotypically normal and four exhibited a balanced translocation identical with that of the parents. A therapeutic abortion was performed in the case of the unbalanced translocation, the two trisomic fetuses, and a male fetus of the haemophilia A carrier mother. After the abortion the prenatal chromosome findings were confirmed by cell cultures from fetal tissues. No immediate complications due to the amniocentesis were recorded, but two term fetuses died antenatally, one child was delivered prematurely, and one pregnancy terminated spontaneously foru weeks after the amniocentesis. Any casual relationship to the puncture was unlikely in these cases. All other pregnancies had a normal course and the outcome was in agreement with the prenatal studies. Although indications for prenatal karyotype analyses are evident in pregnancies at risk due to parental balanced translocation karyotype and advanced maternal age, the need for large-scale screening programmes is questionable, because the decision should be in the hands of the parents.