Objective To explore the indication, advantage and disadvantage of modified or classical technique of intraoral sagittal split ramus osteotomy (SSRO) for correction of mandibular prognathism. Methods From January 1997 to January 2005, 95 patients suffering from mandibular prognathism or accompanied by other deformities were treated with modified or classical technique of intraoral SSRO. Of 95 cases, there were 34 males and 61 females, aging 15 to 44 years, including 53 cases of single mandibular prognathism, 28 cases accompanied with mandibular deviation, 11 cases accompanied with maxillaryretrognathism, 2 cases accompanied with glossacele and 1 case accompanied with malar protrution. X-ray cephalometry showed: sella-nasion-A point(SNA) 80-83°, sella-nasion-B point(SNB) 80-84°, A point-nasion-B point(ANB)-3-1°.Fortythree cases were corrected by modified SSRO and 52 cases by classical SSRO. Results The face appearance and dental articulation of all the patients were improved greatly. In patients by classical SSRO, disorder of local sensibility occurred in 9 cases, mandibular fracture during the cleavage ofthe ascending ramus in 1 case, significant bleeding in 1 case, postoperative infection in 1 case and postoperative relapse in 3 cases. In patients by modifiedSSRO, disorder of local sensibility occurred in 2 cases and postoperative relapse in 1 case; no mandibular fracture, significant bleeding, postoperative infection and other complications occurred. With a follow-up of 3 months to 7 years, X-ray cephalometry showed SNA 81-83°, SNB 78-81°and ANB 1-4°. 〖WTHZ〗Conclusion Modified SSRO is an ideal method of correcting mandibular prognathism, especially severer mandibularprognathism accompanied by mandible deviation deformity.