Since 1972, we have performed 951 early amniocentesis in 902 pregnant women. There were 19 twin pregnancies, all diamniotic, representing 2.1% of the sample. Diagnosis was always suspected before the amniocentesis. It was confirmed by echography in the 14 cases in which this technique was used. Out of the first 5 cases without echography, we punctured only one sac. In the 14 last cases, the process was successful in 13 cases thanks:--the perfection of echography showing the exact location of the fetuses and the position of the septum--the injection of congo red (12 cases) or methylene blue (2 cases) into the first sac. The indications were as follows: chromosomal aberrations (14 cases) metabolic diseases (1 case), sex-linked disorders (1 cases) neural tube defects (3 cases). No complications due to amniocentesis were observed but three abortions and one fetal death occurred. The reason why is discussed. We have made only one therapeutic abortion.