The origin of anomalies in the chromosomal syndromes is believed to be both polyetiologic and polypathogenetic. Whereas some malformations quite clearly appear to result from single gene mutations or from genic imbalance due to individual monosomic or trisomic loci, other anomalies (singly or in complex patterns) are better interpreted as originating from disturbances in particular biochemical pathways which affect the development of a variety of traits. Additional phenogenetic studies and the use of sophisticated biochemical analysis in persons with complex patterns of anomalies should provide a truer understanding of disease mechanisms and provide guidance for future studies which are aimed at the treatment and prevention of these intriguing misadventures of Nature.