The incidence of congenital anomalies is reported to be 2~3% of live born births. In the past, infection was one of the major cause of perinatal morbidity and mortality, but owing to the development of antibiotics and intensive care, congenital anomalies are becoming a major cause of perinatal morbidity and mortality. Prenatal diagnosis of congenital anomalies is becoming more important because appropriate perinatal care may minimize the effect of congenital anomalies. We studied the incidence of congenital anomalies diagnosed by antenatal ultrasound examinations retrospectively. The study group was 13,652 pregnant women who were taken antenatal obstetric ultrasound examinations between Jan. 1, 1991 and Dec. 31, 1995. There were 694 cases of congenital anomalies diagnosed by antenatal ultrasonography examinations. The incidence of congenital anomalies was 5.1%. The most common congenital anomalies by organ system was central nervous system(32.7%), and the next were urogenital (14.7%), heart(11.7%), face and neck(8.4%), multiple anomalies(8.4%), G-I(6.8%), abdominal wall defect(4.5%), skeletal(3.5%), thorax(3.2%) in order. The most common congenital anomalies was choroid plexus cyst(8.8%), and the next were hydrocephalus(7.9%), hydronephrosis (6.5%), cystic hygroma(4.2%), anencephaly(3.9%), cleft lip and/or palate(2.9%), hydrops fetalis(2.4%), small intestinal obstruction(2.3%), multicystic kidney(2.2%), diaphragmatic hernia(2.2%), omphalocele(2.0%), gastroschisis(2.0%), holoprosencephaly(1.9%), ovarian cyst(1.6%), esophageal atresia(1.4%), microcephaly(1.4%), amniotic band syndrome (1.3%), meningocele or meningomyelocele(1.3%) in decreasing order. Ultrasonography may be a useful prenatal diagnostic method of detecting congenial anomalies.