Amniocentesis during the third pregnancy trimenon in case of suspected premature rupture is performed for two reasons: on the one hand, the maturity parameters can be determined as usual from the amniotic fluid, and on the other hand it serves to determine the presence of germs that may have caused the premature rupture. At the same time, it is possible to confirm the suspicion of premature hydrorrhoea gravidarum by instillation of dyestuff into the amniotic cavity. Premature rupture was confirmed in 21 of 65 cases where clinical findings had not supplied safe evidence; in the remaining 44 cases this method permitted the exclusion of premature hydrorrhoea. An evaluation was performed by means of a retrospective study of parturitions between 1975 and 1985 with regard to late amniocenteses in cases of suspected premature rupture, the investigated parameters being the course of pregnancy and of birth, postpartal state of well-being, bacteriological findings in the amniotic fluid, and results of instillation of blue dyestuff.