Background and Purpose: Anomalies of the caval veins are considered to be common cardiac malformations. The knowledge of the varieties of the caval venous system is essential for cardiovascular surgery, pacemaker implantation, intensive care medicine or cardiac catheterization. The authors wanted to know, if anomalies of the caval veins are related to the type and complexity of congenital heart disease. Material and Methods: The records of 1,631 patients who were catheterized between 1991 and 2003 were reviewed. Results: 92 of these had anomalies of either the superior or inferior caval vein. 23 had simple congenital heart disease, while in 69 this was considered to be complex (p < 0.001). Embryologic considerations are discussed. Conclusion: It could be proven that anomalies of the caval veins are more often related to complex congenital heart disease. Embryologic considerations show at least a coincidence of the development of the caval veins and of congenital heart disease. For clinical work with these patients the knowledge of these anomalies is important.