We reviewed a consecutive 143 cases of blunt liver trauma, 43 children and 100 adults, to clarify the pathosis of liver trauma and to reasonably select treatment, non-operative or operative management. The primary determinant in the prognosis of liver trauma was clearly hemorrhage due to vessel injuries and its main treatment method was hemostasis. We developed a new concept for the classification of blunt liver trauma based on vessel injuries: I = subcapsular Glissonian vessel injuries, II = transcapsular Glissonian vessel injuries and III = in-/out-flow vessel injuries and 3 basic types were divided into 2 subtypes, respectively. Distribution of liver trauma according to the present classification was as follows: type I = 23% in child cases and 22% in adult cases, type II = 65% and 64% and type III = 12% and 14%, respectively. The main management was non-operative for type I, minor or major surgery for type II, and extended surgery for type III. The analysis of dead cases showed the following: I = 0% in child cases and 6% in adult, II = 60% and 55%; III = 40% and 39%, respectively. The first direct cause was hemorrhage: 60% in child cases and 49% in adult. The present classification was applicable for both child and adult patients, and presented a selection of management for liver trauma, suggesting the prognosis.