PURPOSE: To evaluate pathologic patterns and outcomes of treatment of a biceps tendon lesion associated with a rotator cuff tear. MATERIALS AND METHODS: We reviewed 92 patients (i) who underwent surgery for a cuff tear, (ii) for whom the biceps lesion could be observed retrospectively, and (iii) had a minimum follow-up of 2 years. The pathology of biceps tendon was classified into 4 types: tenosynovitis, fraying or hypertrophy, tear, and instability. All but the 4 with massive cuff tears were repaired. The biceps lesions were treated with debridement in 30, tenotomy in 10, tenodesis in 8, and recentering in 4. UCLA scoring was used for clinical results. RESULTS: Seventy patients had a biceps lesion, 19 tenosynovitis, 22 fraying or hypertrophy, 21 a tear, and 8 instability. A biceps lesion was observed in 63% of cases of cuff tears below the medium size, and in 88% of cases with cuff tears above the large size. UCLA scores according to the pathology of the biceps lesion were 29.6 in the absence of a biceps lesion, and 28.3 in its presence. UCLA scores in patients with tenotomy or tenodesis for associated biceps tendon lesions were 28.2. CONCLUSION: There is a greater incidence and severity of a biceps lesion with a larger cuff tear. Therefore, the cause of a biceps lesion might be related to the cause of the cuff tear. Among the several options of treatment for biceps lesion, tenotomy or tenodesis may be particularly effective in providing pain relief.