A prospective outcome study to determine the efficacy and complications associated with posterolateral arthroscopic discectomy was initiated in April 1988. One hundred seventy-five patients with symptoms consistent with a lumbar disc herniation and correlative imaging studies were treated operatively, and 169 were available for followup evaluation. Fifty-nine patients with a central herniation or a nonmigrated sequestered fragment were treated using bilateral biportal posterolateral access, whereas 116 patients with radiographic evidence of a paramedial, foraminal, or extra-foraminal herniation were treated using the unilateral uniportal approach. The minimum duration of nonoperative management ranged from 3.5 to 28 months (average, 16 months), and all patients had a minimum of 24 months of postoperative followup. Outcome analysis indicated that 149 procedures were successful, whereas 20 (11.8%) procedures were failures because of persistent radicular symptoms that, in some cases, required open laminotomy. Complications associated with the procedures included one disc space infection, one transient peroneal neuropraxia, and four index extremity skin hypersensitivity. All of these complications resolved without sequelae, and there were no neurovascular complications directly related to the surgical approach.