OBJECTIVE To evaluate the cost-benefit of changing from selective (high risk) to routine ultrasound screening for fetal anomaly. METHODS Women booked by general practitioners for primary antenatal care at their local hospital. METHODS Prospective study of the 12 months before and after introduction of routine second trimester ultrasound for fetal anomaly at our institution. All congenital abnormalities, mode of detection, and outcome were recorded and a cost analysis of the programme attempted. RESULTS In the 12 months of selective (high risk) ultrasound policy, detailed second trimester scans were performed in 1007 (26%) pregnancies. In the 12 months of routine ultrasound anomaly screening, scans were performed in 3529 (93%) pregnancies. Routine ultrasound was the sole method of detection for 11 major and 18 less severe congenital abnormalities found in low risk pregnancies which would not previously have qualified for high risk ultrasound. In seven of these cases the parents opted for termination of pregnancy, with estimated savings on treatment and long term care of 1,015,546 pounds. The financial cost of providing the ultrasound screening service at our hospital for 12 months was calculated at 57,573 pounds and the resulting financial benefit for the year was estimated at 957,973 pounds. CONCLUSIONS Although it is recognised that many of the emotional and psychological costs and benefits of the service are difficult to evaluate, routine fetal anomaly ultrasound would seem to be economically justifiable. The financial savings achieved at our hospital would translate into a potential annual saving for the National Health Service of nearly 170 million pounds if screening were offered in all hospitals in England and Wales.