1. A new operation of body-to-body intervertebral fusion by grafts introduced through a posterior approach is described. This is a preliminary report of early results, with follow-up to two years, which seems to be encouraging.

2. In spondylolisthesis, abnormal mobility of the loose posterior neural arch is believed in itself to cause nerve root pressure, and excision of the arch is an important part of the operation.

3. In the few cases where spinal fusion is needed after removal of a prolapsed intervertebral disc—and the proportion is now very low—posterior intervertebral fusion has proved very satisfactory.