Background: A successful clinical result is reported in 75% to 85% of impingement patients after arthroscopic subacromial decompression. The result is maintained over time, but few studies have investigated the integrity of the rotator cuff in these patients. Materials and methods: Using ultrasonography, we examined the integrity of the rotator cuff in 70 patients 15 years after arthroscopic subacromial decompression. All patients had an intact rotator cuff at the index procedure. Results: Tendons were still intact in 57 patients (82%), 10 (14%) had partial-thickness tears, and 3 (4%) had full-thickness tears. Discussion: The total number of 18% tears (partial and full thickness) in this study, including patients clinically diagnosed with subacromial impingement at a mean age of 60 years, is unexpectedly low compared with 40% degenerative tears reported in asymptomatic adults of the same age. Conclusion: Arthroscopic subacromial decompression seems to reduce the prevalence of rotator cuff tears in impingement patients. This appears attributable to elimination of extrinsic factors such as mechanical wear and bursitis. The potential effect of surgery on intrinsic cuff degeneration is unknown, but intrinsic factors may explain tears still developing despite decompression.