In the 36th week of gestation intrauterine death of both twins occurred in a 31-year old primigravida. The examination of the C- and the D-antigen of the mother's blood (result of previous testing: AB Rhesus negative) immediately before delivery showed a mixed field agglutination which pointed to a fetomaternal macrotransfusion. Fetal haemoglobin in the mother's circulation was 7.8% of her total haemoglobin, so that a fetomaternal haemorrhage of about 440 ml whole blood had to be suspected. For Rhesus-prophylaxis 17 standard doses of anti-D-immunoglobulin were administered intramuscularly distributed over 4 days. No adverse effects were seen; fetal haemoglobin dropped to 2.0% 5 days and to 0.1% 15 days after the beginning of the treatment. A control examination after 9 months showed no signs of a Rhesus-(D)-sensitisation of the patient.