Tibial segmental fractures are considered special type of lesion and pose many problems and the results often are unsatisfactory. We performed retrospective study of the 17 cases of open tibial segmental fracture which were treated from January 1990 to December 1995 and evaluated the efficacy of the external fixation and intramedullary nailing. The segmental fracture were classified according to the Melis classification and open fracture were classified according to the Gustilo-Anderson classification. After average follow-up of 16 months (range, 12 to 24 months), all of the fractures had healded except one. The results were as follows: 1. The average time of union was 22.5 weeks in the case of intramedullary nailing (Endernail; 26 weeks, Interlocking IM nailing; 21 weeks) and 31 weeks in the case of external fixation (Monofixator; 28 weeks, Ilizarov external fixator; 34 weeks). 2. Nonunion and osteomyelitis was developed in one case of Ilizarov external fixation and 5 cases of pin tract infection were also developed. Among 8 cases of external fixation group, 4 cases of delayed union and one case of malunion were developed. 3. In intramedullary nailing, delayed union was developed in 4 cases. 4. The functional results by Tile rating system were showed good in 6 cases, acceptable in 8 and poor 3. In conclusion, intramedullary nailing provided better ressults thanexternal fixator in open segmantal tibial fractures, but we consider fixation device should be selected depending on the fracture type, degree of comminution and condition of the soft tissue.