A Vietnamese couple were both carriers of alpha-thalessemia-1. The woman had a first pregnancy terminated in the delivery of a hydropic fetus due to homozygous alpha-thalassemia. The couple requested prenatal diagnosis for the second pregnancy. The DNA obtained from cultured amniotic fluid cells was studied pregnancy. The DNA obtained from cultured amniotic fluid cells was studied by hybridization with globin cDNA in solution and on filters (Southern technique). Both analyses demonstrated no alpha-globin structural genes were present. Following termination of the pregnancy, the diagnosis was established by the presence of only hemoglobins Barts (gamma 4) and Portland (zeta 2 gamma 2) in the fetal blood.