METHODS Retrospective cross-sectional study of cases with conjoined lumbar nerve root anomalies. OBJECTIVE To provide a description of presenting symptoms and clinical signs of conjoined nerve roots. BACKGROUND Nerve root anomalies are frequently underrecognized on advanced imaging studies and are also underappreciated and underreported when encountered surgically. METHODS In this retrospective cross-sectional study, we report the intraoperative identification of 22 cases of conjoined nerve root anomaly, encountered within a period of 11 years. All cases underwent hemilaminectomy in addition to medial facetectomy and pediculectomy. All patients were followed for a mean duration of 53+/-8.2 months (range, 2 to 108 mo). RESULTS Twenty-two patients had conjoined nerve root anomaly (mean age at diagnosis=47.7+/-5.1). They included 11 cases of L5-S1, 10 cases of L4-L5, and 1 of S1-S2. Twelve patients (54.5%) had symptoms in 2 territories. Straight leg raising sign and crossed straight leg raising were positive in 14 (63.6%) and 7 (31.8%) patients, respectively. All patients returned to work within 2 months after surgery. The signs and symptoms in only 7 cases (31.8%) could be explained by the underlying pathology (disc herniation) alone. In the remaining 68%, the conjoined roots have probably contributed to the incompatible signs and symptoms. CONCLUSIONS Twin dermatomal involvements, in addition to a negative Lasègue sign, are clues to the diagnosis of a probable conjoined nerve root anomaly. Extension of routine hemilaminectomy to a facetectomy and partial pediculectomy leads to a favorable outcome.