The paraspinal posterior approach to the lumbar spine initially was described for spinal fusion, particularly for treatment of lumbosacral spondylolisthesis. Despite the technical details described by Wiltse et al, the exact location of the sacrospinalis muscle that must be split remains unclear. We sought to clarify the anatomic description of the paraspinal posterior approach to the lumbar spine, and to provide topographic landmarks for facilitating this surgical approach. Fifty cadavers were dissected using an anatomic transmuscular paraspinal approach. The level of the natural cleavage plane between the multifidus and the longissimus parts of the sacrospinalis muscle was noted, and measurements were taken between this level and the midline at the level of the spinous process of L4. A natural cleavage plane between the multifidus and the longissimus parts of the sacrospinalis muscle was present in all specimens. There was a fibrous separation between the two muscular parts in 88 of 100 cases. The mean distance between the level of the cleavage plane and the midline was 4.04 cm (range, 2.4-7 cm). Small arteries and veins were present at the level of the cleavage plane in all specimens. These vascular landmarks make it easier to locate the muscular cleavage plane and reach the articular and transverse processes during the paraspinal approach.