A full and detailed review of trophoblast disease at Rome University's Obstetrics and Gynecology Clinic led to a re-examination of some of the classical epidemiological factors in this pathology: age, parity and blood group. The precise incidence of this condition is difficult to establish from hospital series alone. In spite of numerous clinical studies, its aetiology has not yet been fully clarified. The various environmental socio-economic, racial, genetic and other factors, which are sometimes quoted, are too heterogeneous and contradictory to provide significant results. Of evaluated risk parameters, only pregnancy at an advanced age appears to carry increased risk. For these reasons, and given the low incidence of trophoblast pathology, it is recommended that a register of the disease be instituted, at least at Regional level.