A prospective, randomized, controlled, double-blind clinical study was performed to assess the short-term efficacy of local steroid injection for the management of early-stage subacromial impingement syndrome (SIS). 49 patients with early stages (stage I and II) of SIS were included in the study. None of the patients had a full-thickness tear of the rotator cuff. The subjects were randomized to receive either one milliliter containing forty milligrams of triamcinolone acetonide per milliliter with four milliliters of 2 per cent lidocaine without epinephrine (the corticosteroid group) or  five milliliters of 2 per cent lidocaine without epinephrine (the control group). Twenty-four patients, whose mean age was fifty-three years (range, thirty-one to seventy-two years), were randomized to the corticosteroid group, and twenty-five patients, whose mean age was fifty-five years (range, thirty to seventy-four years), were randomized to the control group. The average duration of the  symptoms before the injection was seven months for both groups. All patients participated in a standardized exercise program after the injection. The patients were re-examined every month with regard to the assessment of function and pain. The duration of follow-up was six months. At month 6, the mean active range of flexion, abduction and external rotation improved by 27, 21 and 12 degrees, respectively, for the corticosteroid group and by 16, 9 and 5 degrees, for the control group. Twenty-one patients in the corticosteroid group and twenty patients in the control group had moderate and severe pain before the injection. At month 6, three patients in the corticosteroid group had moderate and severe pain, compared with sixteen patients in the control group. Results of our study suggest that the use of local steroid injections for the management of early-stage SIS can alleviate pain and improve the range of motion of the shoulder in the short term.