Thirty-eight patients with chronic calcifying tendinopathy of the shoulder were randomized prospectively into two groups: 19 patients had endoscopic decompression and 19 had open decompression. Thirty-three patients (19 with open and 14 with endoscopic decompression) were available for followup. Clinical and ultrasonographic investigations were done at followup. The purpose of the current study was to evaluate prospectively the clinical and sonographic results after open decompression and after endoscopic decompression. Apportionment of age and gender was similar in both groups. The followup was 15.7 months for patients after open decompression and 17.1 months for patients after endoscopic decompression. The average Patte score was 84.5 points (84.4 for patients who had endoscopic decompression and 84.6 for patients who had open decompression). Corresponding results were found with a Constant and Murley score of 96.6 points (97.6 for patients who had endoscopic decompression and 95.8 for patients who had open decompression). In the endoscopic group physiotherapy was recommended for 5 weeks more than in the open surgery group. Similar results were seen for the incapacity to work in both groups with 4.6 weeks for the patients who had endoscopic surgery and 5 weeks for the patients who had open surgery. No nerve injuries, wound infections, or other postoperative complications were found. Comparison of both surgical methods showed good clinical and score results. Endoscopic and open surgery are equally effective in the treatment of chronic calcifying tendinopathy.