Fukuyama type congenital muscular dystrophy (FCMD) is an autosomal recessive disorder characterized by a combination of primary muscular dystrophy of early infantile onset and brain malformation (lissencephaly type II). The identification of the FCMD gene locus at 9q31 opened the theoretical possibility of prenatal diagnosis. The authors conducted prenatal diagnosis in two unrelated FCMD families by analysis using nine microsatellite CA-repeat polymorphic markers flanking the FCMD locus, and calculated phenotype probabilities in fetuses with a computer program, LINKAGE. The fetus in family 1 showed a 99% probability of being healthy either as a normal homozygote or a heterozygote carrier and was born without signs of FCMD. In family 2, the fetus was diagnosed to have FCMD with at least 86% probability. The parents of this family decided to terminate the pregnancy and an abortus showed brain malformations characteristic of an FCMD fetus.