Nonimmune hydrops fetalis (NHF) is an abnormal accumulation of fluid - especially serous - in visceral cavities and soft tissues. This condition may be caused by: cardiovascular diseases, chromosomal disorders, infections, lung, stomach, intestinal, kidneys, urinary tract and blood diseases, metabolic disorders and tumors. NHF may by diagnosed by an ultrasound scan. THE AIM of the study was to present diagnostic and therapeutic difficulties as well as management with reference to NHF.An abnormal accumulation of fluid in visceral cavities and subcutaneous tissue of two fetuses was diagnosed by an ultrasound scan. Despite a detailed and specific diagnostic proceeding which included: infections, congenital malformations, chromosomal abnormalities etc. it was impossible to establish the cause of NHF. The symptomatic therapy was performed: periodic cordocentesis with an injection of human albumin solutions. In case of the first fetus therapeutic thoracocentesis was performed. The fetuses were delivered in 32nd and 31st week of pregnancy. Both neonates survived but even after the delivery it was impossible to establish the cause of NHF.Multidirectional diagnostic approach is essential for the implementation of causal treatment of NHF. In case of idiopathic NHF the only management is symptomatic therapy, fetal monitoring and preterm delivery.