We report prenatal diagnostic studies for metaphyseal chondrodysplasia of the Schmid type. Identification of a specific COL10A1 gene mutation in an affected father allowed prenatal diagnosis by chorionic villus sampling in a twin pregnancy. Neither of the nonidentical twins received the abnormal COL10A1 gene from their affected father. This result was confirmed by postnatal DNA analysis. Prenatal diagnosis can be offered to all families with characterized COL10A1 gene mutations.