Posterior lumbar interbody fusion (PLIF) is a standard surgical technique for the lumbar degenerative diseases. However, some problems such as collapse or retropulsion of the grafted bone and pseudoarthrosis have been reported when autogenous or cadaveric bone is used. Two iliac bone blocks with one-side cortex and one dense hydroxyapatite (HA) block were grafted together into the interbody space as in a sandwich. Cancellous bone chips locally harvested were also grafted onto the anterior and lateral aspect of the HA block. Twenty-six patients (12 males, 14 females) who could be followed minimally for 2 years were examined. The surgical outcome of each patient was evaluated by the Japanese Orthopaedic Association Assessment of Treatment of Low Back Pain (JOA score) and the recovery rate. Radiographic evaluation was based on the extent of bony union, the presence of a clear zone in the upper or lower margin of the HA block, cracking of the HA block, sinking of the HA block, and changes in lumbar-sagittal alignment pre- and postoperatively. The overall recovery rate ranged from 42.9% to 100% (mean 88.3%). Bony union was confirmed in 25 patients (96.2%). Clear zone was observed in 9 of 68 contact surfaces (13.2%). Sinking was observed in 8 of 34 segments (23.5%), and cracking of HA block was observed in 6 segments (17.6%). A mean loss of lordosis was found to be 2.4 degrees . The dense HA block is a useful substitute for autogenous bone graft for PLIF.