The purpose of this study was to determine the degree of criterion validity and intra-tester reliability of humeral head palpation in subjects with shoulder pathology. The study also sought to determine whether there was any effect of arm position on humeral head position in subjects with shoulder pathology. In a same day repeated measures design, 27 subjects had the distance between the most anterior portion of the humeral head and the anterior edge of the acromion measured by a radiologist using MRI (supine), and by a physiotherapist using palpation and photography (supine, sit with arm in neutral and in abduction). The Standard Error of Measurement (SEM) for the difference between MRI and palpation ranged from 3.4 to 4.4mm and correlated significantly with palpation measures in sit (r=0.57-0.64, p<or=0.002). The Intraclass Correlation Coefficients (ICCs) and SEMs for intra-tester reliability were 0.85 and 2.6mm for supine, 0.86 and 2.2mm for sit (glenohumeral neutral), and 0.91 and 3.0mm for sit (glenohumeral abduction). Significant differences between the positions of sit neutral and sit with abduction were found (p<0.001). Humeral head palpation in sit abduction demonstrates sufficient validity and reliability for clinical use.