48 patients with subacromial impingement syndrome (SIS) were randomized to receive a single subacromial injection of either the nonsteroidal anti-inflammatory drug (NSAID), ketorolac, or the corticosteroid, triamcinolone, in order to determine which of the two was more effective in improving shoulder pain and function. Following assessments over a 4 week period, patients who received the NSAID injection improved significantly more than the corticosteroid group, in terms of overall UCLA shoulder rating scale scores and passive abduction. VAS pain scores improved more in the NSAID group as well, but this difference did not reach significance.