Midtrimester amniocentesis was performed on 2,100 consecutive patients over a four-year period. A specially designed ultrasonic aspiration transducer was used to guide the needle into the amniotic cavity under direct vision by following the path of the needle tip ultrasonically as it entered the fluid. This technique has made the aspiration of amniotic fluid relatively simple and safe. We obtained an adequate amount of amniotic fluid in 99.2% of the patients at their initial visits. The incidence of grossly bloody taps was 0.8%, and the total number of bloody amniotic fluid specimens was 2.37%. The rate of primary culture failure was 0.53%. The total fetal loss within eight weeks after amniocentesis was 0.9% as compared with 0.52% in a control population composed of pregnant women between 16 and 24 weeks of gestation. The estimated amniocentesis-related fetal loss was 0.38%.