According to the concept of hybirds of simple, clamp, and ring fixators,we modified the AO/ASIF tubular device into a modified AO/ASIF fixator I. The biomechanical studies for axial compression, tension, anterior-posterior bending, and medial-lateral bending showed that the four characteristics of the modified AO/ASIF fixator I are significantly superior to the Hoffmann and AO/ASIF devices.Between July 1992 and December 1993, 31 consecutive tibial fractures were treated using the modified AO/ASIF fixator I. Early follow-up of 11-17 months showed that all fracture healed. The time of fixator removal was 16-32 weeks, averaged 22. 2weeks. In treatment of segmental fractures, the modified AO/ASIF fixator I gave more improved results over others among simplicity of frame,simplification of operation, and relibility of mechanical quality.