We report on the successful intrauterine surgical treatment of a twin pregnancy with an acardiac fetus. At 18 weeks of gestation the patient presented with polyhydramnios and a hydropic acardius acephalus and the donor twin showed signs of congestive heart failure. Colour Doppler ultrasound allowed localisation of the communicating vessels running on the placental surface towards the umbilicus of the acardiac twin. At 20 weeks we performed endoscopic laser coagulation of the umbilical vessels of the acardiac twin. A sheath (9.8 Charriere) with a 1.9 mm diameter rigid fetoscope (field of vision 60 degrees) was introduced percutaneously under local anesthesia into the amniotic cavity of the "pump" twin. Under sonographic control the fetoscope was directed towards the communicating vessels on the placental surface. A Nd-YAG laser (0.4 mm diameter fiber) was used to coagulate two vessels, artery and vein, until interruption of the reversed arterial perfusion was accomplished. Tricuspid regurgitation of the normal twin disappeared throughout the following two weeks and no further complications occurred throughout pregnancy. At 39 weeks a healthy girl was delivered vaginally. No at the age of 3 months she is developing normally. Minimal invasive endoscopic laser coagulation of the umbilical vessels of the acardiac twin appears to be the optimal currently available treatment for the normal twin, for which otherwise a high mortality ( > 50%) and morbidity must be expected.