In summary, there are a number of conditions where genomic imprinting effects are recognized to be associated clinical disorders of importance in humans. There may be many more. Genomic imprinting should be suspected in any disorder with overgrowth, undergrowth, or behavior abnormalities. Disorders with unusual pattern of inheritance should be studied for the possibility that genomically imprinted gene(s) are involved. Understanding the mechanisms of genomic imprinting has major ramifications in terms of recurrence risk, prediction of whether offspring will be affected, and risk of malignancy. Of particular concern is the potential for uniparental disomy when trisomy is found during prenatal diagnosis.