Extreme lateral disc herniations in the authors' series account for 10% of all lumbar herniations; 80% occurred at the L3, L4 and L4, L5 interspaces. The authors review the clinical findings in 138 patients and point to the characteristic features of the clinical syndrome. They compare the accuracy of various diagnostic studies and conclude that computed tomography is highly accurate and should be used before other diagnostic studies. Discography is still helpful as a confirmatory study in some cases, whereas myelography is particularly useful in disclosing other associated lesions. Analysis of the operative series revealed a high percentage of extruded fragments (60%) and a significant number of double herniations on the same side and at the same level (15%). These two findings may respectively preclude chemonucleolysis and microsurgery from the surgical management of extreme lateral herniations. Double herniations explain some discrepancies in the clinical picture and are emphasized as a potential source of error in diagnosis. The surgical technique allows exploration for herniations within the intervertebral canal as well as for extraforaminal herniations without sacrifice of the facet. Operative results are presented.