A long-term retrospective study (minimum 5 years) was done looking at three groups of anterior cruciate deficient knee patients using both subjective and objective anterior cruciate tests. Twenty-seven chronic anterior cruciate ligament deficient knees reconstructed with the middle third of the patellar tendon and 28 chronic anterior cruciate ligament deficient knees reconstructed with the semitendinosus tendon were included in this consecutive group of patients and were felt to be directly comparable. It was found that the chronic anterior cruciate ligament deficient group reconstructed with the semitendinosus tendon had 4 excellent, 10 good, 7 poor, and 7 failures with an objective score averaging 4.5 of a possible 12, while the comparable group reconstructed with the middle third of the patellar tendon had 16 excellent, 7 good, 3 poor, and only 1 failure with a score of 10 of a possible 12 (P < 0.0032). For completeness sake, 20 anterior cruciate deficient knees from this group of consecutive patients that were reconstructed acutely with the semitendinosus tendon were also examined. This group had 8 excellent results, 9 good, 3 poor, and no failures with a score of 9.8 (P < 0.03 compared to the other group using the semitendinosus tendon). This comparison between the two groups where the semitendinosus tendon was used in the anterior cruciate ligament reconstruction was made only to show the difference between studies dealing with knee reconstructions. There may be a significant difference between a study dealing with acutely reconstructed knees versus one focusing on chronically reconstructed knees, most likely because of both patient selection and time between injury and reconstruction. Subjectively, the activity forms gave postreconstruction activities of 112 of 200 for the chronically reconstructed group using semitendinosus tendon, 115 for the chronically reconstructed group using the middle third of the patellar tendon, and 150 in the acutely reconstructed group using the semitendinosus tendon. The subjects rated their knee 6.2 (chronically reconstructed with semitendinosus), 6.4 (chronically reconstructed with middle third patellar tendon), and 7.9 (acutely reconstructed with semitendinosus) on a scale of 0 to 10. This paper will point out the superiority of using the middle third of the patellar tendon over the use of the semitendinosus tendon in chronically unstable knees. The semitendinosus tendon should not be used even with extraarticular augmentations. The data for the semitendinosus tendon in acute anterior cruciate ligament reconstruction is included to show how different two groups of patients can be based on the time of reconstruction from the date of injury.