Purpose : We evaluated both the patients and the normal volunteers to determine the diagnostic criteria ofsubacromial impingement syndrome. Materials and Methods : We analyzed the radiologic finding of Thirty degree ofcaudal tilt view (TCTV) and Supraspinatus outlet view (SOV) of 100 shoulders from 85 patients with clinicallyproved subacromial ipingement syndrome and normal 100 shoulders from 60 volunteers. Result : In TCTV, theprotrusion of acromion below the line of extension from inferior surface of clavicle was shown in 94% of thepatient group and 48% in normal group. Sharp tip of acromial protrusion was detectable in 55.3% of the patientgroup and 10.4% in normal group. In SOV, curved type of acromion was seen in 53% of the normal and 50% in patientgroup. Hooked type of acromion was deteted in 3% and 31% of the normal and patient group, respectively. Conclusion: Protrusion of acromion at TCTV itself was not a criteria of subacromial impingement syndrome, but more than 7mmbelow the line of extension from inferior surface of clavicle was meanigful. In SOV, hooked type of acromion was acriteria of subacromial impingement syndrome but curved type is was not a finding of diagnostic significence.Acromial spur formation on TCTV and SOV was important criteria of subacromial impingement syndrome.