The indications, technique, and potential complications of the now commonly used obstetric procedure, amniocentesis, have been reviewed. Although amniocentesis is considered by many a routine and a very safe procedure, there are potential complications, especially for the fetus, but for the mother as well. The frequency of these complications can be reduced by meticulous attention to technique and especially by preliminary placental localization. The latter is probably best accomplished by the ultrasound B scan. Because there are potential complications, the indications and timing of amniocentesis must always be carefully weighed before it is carried out.