The reliability of sonography and peritoneal lavage in assessing the need for immediate surgical intervention in blunt abdominal trauma was examined in a prospective study (n = 71). Statistical analysis revealed a sensitivity of 100% for peritoneal lavage compared to 84% for sonography; the accuracy was 99% versus 86%, the predictive value 97% vs. 89%. The statistical difference was significant (p less than 0.05). The results demonstrate that sonography cannot replace peritoneal lavage in the diagnosis of blunt abdominal trauma. The discussion of the advantages and disadvantages of both methods shows that sonography and peritoneal lavage are not competing, but rather, are complementary examinations.