STUDY DESIGN A prospective, randomized controlled trial. OBJECTIVE To investigate the effect of the lateral decubitus position, after a caudal epidural injection, on outcome. SUMMARY OF BACKGROUND DATA Caudal epidural injections are used widely in the treatment of low back pain and radicular leg pain. Various measures have been used to improve the efficacy of these injections in previous studies. Our aim was to investigate the effect of the lateral decubitus position, after administering a caudal epidural injection, on outcome. METHODS Fifty-seven patients undergoing caudal epidural injection for low back pain associated with radicular leg pain were randomly allocated into 2 groups. Group 1 (treatment group) had 28 patients who were placed in the lateral decubitus position after injection. Group 2 (control group) had 29 patients who were laid supine after injection. Patients were assessed before injection using the Verbal Pain Score (VPS) and the Oswestry Disability Index (ODI). They were reassessed after 6 weeks using the same outcome measures. RESULTS Both groups demonstrated improvement after injection. The degree of improvement in the VPS was significantly greater in group 1 compared with group 2 (P = 0.00007). The degree of improvement in the ODI was not statistically significant (P = 0.14). CONCLUSION Laying a patient on the side of their leg pain after a caudal epidural injection has a beneficial effect on the degree of pain relief. We recommend that this simple and safe maneuver be introduced routinely after administering a caudal epidural injection, to aid in the eventual outcome of a potentially difficult clinical problem.