1. Fifty cases of complete or partial agenesis or malformation of the sacrum with associated anomalies have been reported. These include members of the Mexican, Negro, and white population.
2. In thirty-two cases reported there is complete absence of the saerum and coccyx, and in eighteen there is partial absence or malformation of the sacrum and coccyx.
3. Vertebral defects in these patients range from complete absence of the spine below the twelfth thoracic vertebra to minor malformations.
4. Associated anomalies include spina bifida; meningoccle; club-foot; paralysis; atropiry; contractures dislocated mips; arthrogryposis; bladder or bowel dysfunction or both; anal defects; eleft lip or eleft palate, or both; and herniae. Other concomitant anomalies present are reported.
5. Possible related, contributing eiological factors such as complications of pregnaney, diabetes mellitus in the probands' spontaneous abortions, and types of gestation and deliveries are presented.
6. Anomalies in collaterals and ascendants are reviewed.
7. Spontaneous and artificial production of spine anomalies in animals and their genetic implications have been discussed.