Eighty-five patients with knee injuries were included in a 4 month retrospective study that compared the relative accuracy of the Lachman test, the anterior drawer sign, and the pivot shift test. All examinations were performed under anesthesia and followed by arthroscopy, which confirmed 22 injuries. Of all ACL injuries occurring within 2 weeks of arthroscopy (N = 9), the pivot shift test was the most sensitive (88.8%), followed by the Lachman test with a 77.7% sensitivity. The anterior drawer sign was the least sensitive at 22.2%. All had specificities more than 95%. For all injuries of more than 2 weeks (N = 13), the Lachman and pivot shift tests were 84.6% sensitive, while the anterior drawer sign increased to a sensitivity of 53.8%. Again, all were specific to more than 95%. For all ACL injuries, irrespective of age, the Lachman test was 81.8% sensitive and 96.8% specific; the anterior drawer sign was 40.9% sensitive and 95.2% specific; and the pivot shift was 81.8% sensitive and 98.4% specific. The data support an accurate preoperative diagnosis in ACL deficient knees when the Lachman and pivot shift tests are positive, and essentially rules out this type of injury when these tests are negative. The anterior drawer sign, although widely used, is a poor diagnostic indicator of ACL injuries, especially in the acute setting.