The evaluation of patients with multiple congenital anomalies (MCAs) is of critical importance because all unbalanced autosomal chromosomal aberrations and most gene mutations and teratogens produce syndromes. Therefore, MCAs are sensitive indicators of germinal mutagens and teratogens. The delineation of an MCA-entity facilitates a better understanding of the phenotypic spectrum, prognosis, and origin of the condition. The latter may be of great importance in genetic counseling or to detect new teratogenic agents. Gene mapping efforts for some of these conditions might become feasible after the identification of informative families.