The increasing use of amniocentesis requires that the technique be made as safe as possible. The results of 284 amniocenteses done under ultrasound control are presented and compared with the results of 140 amniocenteses performed without ultrasound control. The use of ultrasound guidance increased the success rate from 80 to 99.6 per cent and decreased the incidence of feto-maternal haemorrhage from 8.5 to 2.8 per cent. The incidence of blood-stained amniotic fluid was reduced from 43.5 to 17.6 per cent. The clinical significance of these findings is discussed and the results interpreted as indicating that amniocentesis done with ultrasound guidance is a safer and less traumatic procedure.