STUDY DESIGN: Prospective longitudinal clinical study. OBJECTIVE: The purpose of our article was to investigate the clinical outcomes with type and level of disc herniation in a young, active population undergoing lumbar microdiscectomy. SUMMARY OF BACKGROUND DATA: There are few reported outcomes studies on the relationship between disc herniation level, type of disc herniation, and surgical outcomes of lumbar microdiscectomy in a young, active population. METHODS: One hundred ninety-seven (197) consecutive single-level lumbar microdiscectomies performed by a single surgeon were prospectively followed over a 3-year period. All patients had failed a period of nonoperative care including physical therapy and/or transforaminal epidural steroid injections. One hundred eighty-three patients (139 males, 44 females) with a mean age of 27.0 years (range 19-46 years) were prospectively followed for a mean of 26 months (range, 12-38 months). Outcomes were assessed using Visual Analog Scale (VAS), Oswestry disability index, patient satisfaction, return to military duty, and need for additional surgery. The type of disc herniation (contained, extruded, or sequestered) and the lumbar level of herniation were also recorded. RESULTS: At final follow-up, 84% (154 of 183) of patients had returned to unrestricted military duty; 16% (29) had been medically discharged. The mean decrease in VAS leg pain score was 4.7 points (from mean preoperative 7.2 to mean postoperative 2.5); 80% (146) reported a decrease of greater than 2 points. The mean Oswestry index improved from 53.6 before surgery to 21.2 at final follow-up. Overall, 85% (156) were satisfied with their surgery. Six patients had recurrent herniations (3%) with 4 of the 6 undergoing additional surgery. Patients with preoperative VAS scores consistent with a preponderance of radicular leg pain versus back pain demonstrated better surgical outcomes in all categories (P < 0.001) When classified by disc herniation type, sequestered discs at all levels demonstrated better Oswestry and VAS scores versus extruded or contained disc herniations. (P < 0.001) Disc herniations at the L5-S1 level had significantly greater improvements in both mean VAS leg and Oswestry outcome scores than disc herniations at the L4-L5 level. (P < 0.001) Preexisting restricted duty status at time of first surgical consultation was associated with poorer outcomes. Smokers had a significantly lower return to full active military duty (P = 0.037). CONCLUSION: Microdiscectomy for symptomatic lumbar disc herniations in young, active patients with a preponderance of leg pain who have failed nonoperative treatment demonstrated a high success rate based on validated outcome measures, patient satisfaction, and return to active duty. Patients with disc herniations at the L5-S1 level had significantly better outcomes than did those at the L4-L5 level. Patients with sequestered or extruded lumbar disc herniations had significantly better outcomes than did those contained herniations. Patients with contained disc herniations, a predominance of back pain, on restricted duty and smoking should be counseled before surgery of the potential for less satisfaction, poorer outcomes scores, and decreased return to duty rates.