A survey of human cytogenetics has been presented, including a discussion of terminology, normal karyotype, and the classic sex chromosome anomalies as well as a description of the autosomal trisomy and deletion syndromes. Several rare cases have been reported to illustrate translocation, double aneuploidy, pericentric inversions, and ring chromosome. The importance of chromosome defects in orthopaedics has been noted, and reasons have been given for believing that these aberrations may constitute a major cause of morbidity and mortality in man.