PURPOSE: We wanted to assess the accuracy of ultrasound for detecting abnormality of the long head of the biceps tendon in patients with rotator cuff disorders. MATERIALS AND METHODS: Between January 2006 and March 2007, we reviewed the arthroscopic findings of biceps tendons in 67 patients with rotator cuff disorder and who underwent ultrasonography pre-operatively. The patients' average age was 58 years and there were 41 males and 26 females. The statuses of the biceps tendons were described as 'normal', 'dislocation', 'subluxation', 'partial or complete tears', and 'tendinopathy'. We investigated the correspondence between the arthroscopic and ultrasonographic findings. RESULTS: On ultrasonography, the biceps tendons were 'normal' in 37 patients and 'abnormal' in 30 patients. On arthroscopy, 5 biceps tendons turned out to have partial tears, which were 'normal' on ultrasonography. On the other hand, 8 biceps tendons were 'normal' which were 'abnormal' on ultrasonography. Three dislocations and 4 complete tears of biceps tendons were identified on arthroscopy, and all of them were detected by ultrasonography. Of the 20 cases of 'tendinopathy' seen on ultrasonography, 15 patients had partial tears and the remaining 5 patients were normal on arthroscopy. CONCLUSION: Ultrasonography is accurate for detecting some biceps pathologies, such as dislocation or complete tear, but it is not accurate for the detection of partial tear.