A mictodeletion of chromosome 22q 11.2, which is the most common human deletion syndrome, has a wide phenotypic spectrum that involves a congenital heart defect, cleft palate or thymic hypoplasia identified at ultrasound examnination, The cases of 22q 11.2 deletion occur as a de novo event or can be inherited as an autosomal dominant. Fluorescence In situ hybridization (FISH) was performed to detect the 22q 11.2 deletion in 64 amniotic fluid samples referred to the Institute of Reproductive Medicine and Population, Medical Research Center, Seoul National University. The abnormal ultrasonographic finding was the most common reason for referral. The 22ql1.2 microdeletion was detected in 4 cases among 64 cases, all presenting heart anomaly by the ultrasonographic finding. The 22ql1.2 FISH testing is a useful diagnosis method in pregnancies with heart anomaly and may also be helpful in genetic counseling.