We evaluated the clinical outcome of arthroscopic acromioplasty and debridement in 162 patients who had either normal rotator cuffs, grade 1 (frayed tendon) partial-thickness tears, or grade 2 (less than 50% of the tendon) partial-thickness tears. The mean time from surgery to the response to the L'Insalata outcome questionnaire was 52.7 months (4.5 years) among the 105 respondents (107 shoulders). The mean score was 90 points; eight patients (8%) scored less than 70 points (range, 30 to 65.5), and their treatment failed early on. The patients with grade 2B (bursal) partial-thickness rotator cuff tears had a significantly higher failure rate (38%). Although the clinical outcome of patients with partial-thickness tears of the rotator cuff comprising less than 50% of the tendon (grade 1 and 2) was not significantly different from that of patients without partial rotator cuff tears, the subgroup of patients with grade 2B partial tears had a statistically significantly higher failure rate and may have been better served with primary repair. With follow-up to 10 years, there was no evidence that clinically relevant or symptomatic intrinsic rotator cuff pathologic conditions progress in those patients with partial-thickness tears treated with arthroscopic anterior acromioplasty.