A new method for measuring the anterior translation in the shoulder joint by dynamic ultrasound was evaluated. We placed a 3.5-MHz transducer on the shoulder anteriorly. By using 3 bony landmarks, we then measured the anterior translation of the humeral head with a force of 90 N applied posteriorly. We performed such measurements in 20 subjects with healthy shoulders and in 20 patients with unilateral shoulder instability. There was a mean translation of 1.9 mm in healthy shoulders and 4.9 mm in unstable shoulders (P < .01). The mean difference between the 2 sides in subjects with normal shoulders was 0.7 mm, whereas the mean difference in patients with instability was 2.8 mm (P < .01). The normal shoulders were examined by 2 examiners to determine the degree to which different examiners' measurements might vary. Although one examiner recorded higher values than the other, the new method seems suitable for measuring increased laxity in unstable shoulders.