This study was aimed at investigating the role of US in the newborn with a clinical suspicion of hemoperitoneum. Hemoperitoneum is a dramatic clinical event which may be caused by some obstetrical and fetal factors--breech or complicated delivery, hepatomegaly, macrosomy, anoxic liver congestion being the most frequent causes. Direct or indirect trauma of an abdominal organ during delivery represents the major pathogenetic factor. Clinical symptoms are correlated with the appearance of shock whose intensity is proportional to trauma severity: symptoms may appear even 48 hours after delivery. The authors report their experience with 4 consecutive cases of neonatal hemoperitoneum which underwent US of the abdomen 24 to 72 hours after birth. In the first 3 newborns, US was performed on the basis of a clinical picture of bleeding shock, while in the extant newborn US was performed after a sudden increase in blood transaminase level associated with an obstetrical paralysis of the left arm. The US examinations were performed using a 7.5-MHz sectorial probe unit (Siemens). In all patients, US demonstrated the presence of a liquid effusion in the abdomen which could be referred to hemoperitoneum. In two patients, it was associated with a traumatic focal alteration of the liver parenchyma, in the third with a diffuse subcapsular liver hematoma and, finally in the fourth patient with a disconnected splenic vascular pedicle which was at surgery demonstrated. In conclusion, US is indicated as the most reliable and valuable diagnostic technique in the study of neonatal hemoperitoneum. The authors believe abdominal US to be essential in all the neonatal cases where hemoperitoneum is suspected and in selected cases presenting specific risk factors, to allow a rapid diagnosis and better treatment planning.