Object. The purpose of this study was to correlate lumbar ultrasound (LUS) and MRI findings in patients suspected of having occult spinal dysraphism (OSD). Methods. Over a 5-year period, 1273 consecutive infants underwent an LUS study at a major pediatric tertiary referral center. Of these, 106 patients had abnormal LUS findings suggestive of an OSD, and 103 underwent subsequent MRI studies. The anatomical descriptions of the 2 studies were compared for agreement. Results. The average age of the infants was 34 days at the time of the LUS study; OSD was suspected in these patients because of the presence of cutaneous stigmata and congenital defects. The most common anatomical descriptions from the LUS study included a thickened or fatty filum (32 cases), filum cyst (11 cases), and presence of a terminal ventricle or syrinx (9 cases). Using MRI findings as the standard reference, the sensitivity of LUS in detecting a thickened or fatty filum was 20%. The sensitivity of detecting an abnormal conus level at or below L-3 was 76.9%. Conclusions. In the patient population chosen to undergo LUS studies, abnormal findings had poor sensitivity at detecting anatomical findings consistent with OSD..