Recent dramatic advances have been made in our understanding of the genetic basis of diseases. One result will be an increase in the number of pregnant women considered potential candidates for prenatal diagnosis. At the same time, the invasive techniques by which fetal specimens for prenatal diagnosis are obtained have come under increasing scrutiny in the lay press. Practicing obstetricians must have sufficient knowledge of the benefits, risks, and limitations of these techniques to respond to patient inquiries. This article reviews the commonly used invasive prenatal diagnostic methods, including amniocentesis, chorionic villus sampling, and fetal blood sampling, as well as less widely available techniques, such as fetal skin and liver biopsies. Such relevant issues as indications, timing, and fetal risks are covered.