PURPOSE: To evaluate the effectiveness of a blocking screw in intramedullary nailing at the tibia proximal shaft fracture. MATERIALS AND METHODS: 63 tibia proximal shaft fractures from January 2000 to December 2002 treated with only intramedullary nailing were referred to as group I, and 8 fractures from January 2003 to December 2003 treated with both intramedullary nailing and the blocking screw were referred to as group II. Retrospective studies were done for group I and II. The incidence of nonunion and the postoperative angular alignments were compared. Malalignment was defined as an angle of 5 degrees anteroposteriorly or mediolaterally. RESULTS: There were 7 nonunion (11%) in group I in compare with none in group II. There were 21 angular malalignments (33%) in group I and 1 in group II (12%) and most of them had valgus deformity or anterior anglulation. No complications were directly due to the use of the Blocking screw. CONCLUSION: The technique of the blocking screw used to be one of the option for proximal tibial nailing at tibial proximal shaft fracture helps to overcome angular malalignments of bones.