The purpose of this study was to evaluate the clinical outcome after 1-stage reconstructions of the anterior and posterior cruciate ligaments (ACL, PCL) with reconstruction of the posterolateral corner (PLC) structures using autogenous hamstring grafts in chronic knee injuries. Prospective case series. We reviewed 17 patients (13 men and 4 women) with chronic multiligamentous injuries after a minimum follow-up of 2 years (range, 24 to 66.3 months). Arthroscopically assisted combined ACL/PCL reconstructions with autogenous semitendinosus-gracilis tendon grafts were performed using the single-incision endoscopic ACL technique and the single femoral tunnel, single-bundle transtibial tunnel PCL technique. The PLC was reconstructed with a free autogenous semitendinous tendon graft. The primary outcome measures were the International Knee Documentation Committee (IKDC) score and stress radiography. As secondary outcome measure, all patients were evaluated with a subjective questionnaire, physical examination, radiologic assessment, and KT-1000 arthrometer testing. The mean time from injury to the reconstructive procedure was 70.2 +/- 96.7 months (range, 5.1 to 312.6 months). At final IKDC evaluation, 4 patients (29.4%) were graded level B (nearly normal), 10 patients (58.8%) level C (abnormal), and 2 patients (11.8%) level D (grossly abnormal). The mean postoperative subjective IKDC score was 71.8 +/- 19.3 points. Mean posterior tibial displacement as measured through stress radiography at 90 degrees of knee flexion was reduced from -15.06 +/- 4.68 mm preoperatively to -7.12 +/- 3.37 mm postoperatively (P < .001). Mean anterior tibial displacement was 0.94 +/- 2.75 mm preoperatively compared with -1.59 +/- 3.50 mm postoperatively (P < .01). Three patients had a fixed posterior tibial subluxation (posterior tibial displacement < or = -3 mm on anterior stress radiographs) postoperatively. Severe subjective instability was reduced significantly by the operative procedure (P < .001). The mean postoperative total anterior-posterior side-to-side difference with the KT-1000 arthrometer testing was 2.00 +/- 2.23 mm (range, -4 to 7 mm). Combined chronic ACL/PCL/PLC instabilities can be successfully treated with 1-stage arthroscopic cruciate ligament reconstruction combined with PLC reconstruction using autogenous hamstring grafts. Although current reconstruction techniques are not able to restore normal tibiofemoral kinematics, most patients recover a functionally stable knee and have considerably improved knee function compared with their preoperative status, based on subjective parameters and objective criteria. Level IV, case series, no historical or control group.