Prenatal genetic studies on amniotic fluid samples obtained early in pregnancy are becoming part of clinical obstetric practice. Most identifiable chromosomal abnormalities and more than 40 biochemical disorders can now be diagnosed in utero, aside from the important fetal sexing in sex-linked diseases. Our experience with 100 consecutive amniotic fluid samples from 94 pregnancies is described. A diagnosis was made from 99% of the amniotic fluids received, with only one sample lost to contamination. Four confirmed affected fetuses were diagnosed prenatally. Abortion followed amniocentesis in 1 case, and a probably unrelated fetal death occurred in another. No errors have become apparent in the outcome of 58 pregnancies. Obstetricians are urged to consider the indications for amnioccntesis for genetic disorders in every patient.