The intrauterine death of one fetus in the case of multiple pregnancies can have an impact on the development of the surviving twin. Based on a single-centre retrospective personal study of 248 multiple pregnancies, 10 of which presented a monofetal intrauterine death, the authors observed the type of placentation, the age and cause of the death, the way in which pregnancy continued and the outcome of the surviving twin. This investigation also includes a review of published documents. Monochorial pregnancies were more frequently encountered in the case of monofetal death in utero. The etiology of the death was not always found and one surviving twin presented lesions as microcephaly convulsions and was retarded on a psychomotor level. In this series these complications did not exist when the pregnancy was bichorial. The authors conclude by demonstrating the major risk of fetal contamination for a live twin coexisting with a dead twin in the case on monochorial pregnancy. Other parameters (cause of death, gestational age at death, delay and duration of cohabitation), do not seem to be significant. It would appear to be of fundamental importance to establish an accurate diagnosis of placentation and to implement specific surveillance of monochorial pregnancies. A decision tree is suggested for use in the case of monofetal death.