This prospective outcomes study was designed to prospectively investigate the outcome of the microfracture technique when applied to full thickness chondral lesions of the knee in a group of athletes. From 1991 to 1999, 109 patients were treated using the microfracture technique. We prospectively followed up 53 athletes who satisfied our inclusion criteria. Average age was 38 years (range 19-55) and mean follow-up was 72 months (range 36-120). Etiology, clinical signs, symptoms and activity level were noted preoperatively and at final follow-up. Lysholm, Tegner, IKDC and functional tests were utilized. Intraoperatively, location, size of the lesions and associated pathologies were recorded. Roentgenograms, MRI or CT scan were done before treatment and at final follow-up. Etiologic factors were mostly related to sports microtrauma (37.5%) and macrotrauma (21%), while 37.5% of our patients did not report any traumatic etiology and 4% showed patellar malalignment. The most common location was medial femoral condyle (61%). Knee pain and swelling improved in 70%, tibiofemoral crepitus in 60%. Hop test was normal in 70% at final follow-up. Subjective evaluation was 40/100 preoperatively and 70/100 at final follow-up. Lysholm was 56.8 preoperatively and 87.2 final. IKDC revealed: 0 A, 3 B, 40 C and 10 D preoperatively while at final follow-up 70% scored A or B. Tegner improved at 2 years from 3.2 to 6; however, at final follow-up 80% showed a decline in sport activity level (Tegner 5). Microfracture technique can offer clinical, functional and subjective improvement in athletically active patients. However because of the decline in sports participation over time, microfracture may not be the definitive procedure for the athlete's knee and other procedures may be indicated in the future.