A new simple and portable arthrometer, the Rolimeter, was used to assess the anterior laxity of knees in 20 normal subjects and 18 subjects with chronic anterior cruciate ligament (ACL) deficiency. The subjects were tested by one examiner using maximum manual force. In order to assess the reliability of the device the same subjects were tested with the KT-1000. In ACL-deficient knees the absolute translation and the side-to-side difference did not differ significantly between the devices. In normal knees the Rolimeter measured slightly smaller translations than the KT, but with a high degree of correlation between devices. If a 3-mm or greater side-to-side difference is considered indicative of ACL deficiency, both arthrometers were successful in diagnosing 16 of 18 cruciate ruptures (sensitivity 89%) and 19 of 20 normal knees (specificity 95%). We conclude that the Rolimeter, when compared with the KT-1000, provides a valid measure of anterior knee laxity.