Low back pain and sciatica is one of the most frequent and troublesome problem in the orthopedic field. A study of the effectivity and reliability of the anterior interbody fusion with autoiliac bone graft for the spondylogenic and Discogenic back pain was done on 166 patients who had been hospitalized from January 1978 to December 1984. The approach to the lesion was retroperitoneal with anterior approach. The anterior interbody fusion was performed by using one block or two block from autoiliac bone. The status of the spine fusion after operation was decided by the plane roentgenogram or clinical sign, and the tomogram or dynamogram in some case. We analysed 116 patients having anterior fusionto study whether fusion rate has any relation with the number of the grafted bone, preoperative diagnosis and the level of fusion. At 9 months after operation, the clinical result was assesed and was compared between the group of the preoperative diagnosis. The following results were obtained from analysis of the cases studied. 1. The fusion rate for the grafted bone was 92.2%. There was no difference in fusion rates between the group of patients operated using one block and two-block. 2. The fate of the grafted bone could be categorized into 5 different types. 3. In patients with spondylolisthesis or spondylolysis, there was high incidence of non union.Also in terms of the vertebral level, the fusin between the L5-Sl showed high incidence of non union. 4. High fusion rate was obtained by using back brace without cast immobilization. The average duration of brace wearing was 6.6 months. 5. Overall clinical results were as follows:excellent or good 64.6%, fair 31.9%, poor 3.5%,and spondylolisthesis showed better clinical results than other diseases. 6. Post sympathectomy symptoms were noticed in 12 patients after operation and there were no permanent genitourinary problem.