OBJECTIVE: To assess the anatomical relationship between spinous process of the lumbar vertebrae and iliolumbar ligament from a viewpoint of surface anatomy. METHOD: Fourteen iliolumbar ligaments of seven human cadavers were dissected and measured distance from the lumbar spinous process to the iliolumbar ligament and vertical depth of iliolumbar ligament from the skin surface. RESULTS: All 14 iliolumbar ligaments were originated at the L5 transverse process and inserted in anterior surface of the iliac crest. Direct distance from lumbar spinous process to the origin siteof the iliolumbar ligament was 7.67+/-0.39 cm(distance from the spinous process to presumed skin point of the termination site of the ligament, 6.71+/-0.4 cm). Vertical depth from skin surface was 3.94+/-0.57 cm to the origin site of the iliolumbar ligament, and 3.67+/-0.54 cm to the termination site of the iliolumbar ligament. CONCLUSION: The iliolumbar ligament was deep seated anatomical structure in the lumbosacral region. Superficial landmark of the lumbar spinous process may be useful in approach to iliolumbar ligament.