The clinical use of digital levels, for joint measurement, may be a viable alternative to standard goniometry. The purpose of this study was to determine the intra- and intertester reliability of a construction grade digital level compared to the standard universal goniometer for measurements for active assisted shoulder range of motion (ROM). Two experienced physical therapists measured shoulder flexion, external rotation (ER), and internal rotation (IR) ROM bilaterally, on two different occasions, in 20 patients (9 males, 11 females, 18-79 years old) with unilateral shoulder pathology, using a goniometer and a digital level. Relative reliability was assessed by using intraclass correlation coefficients (ICC), and absolute reliability was assessed by using 95% limits of agreement (LOA). Intratester ICCs ranged from 0.91 to 0.99, and LOA ranged from 3 degrees to 9 degrees for measurements made with the goniometer and digital level. Intertester ICCs ranged from 0.31 to 0.95, and LOA ranged from 6 degrees to 25 degrees . For the comparison of goniometric vs. digital level ROM, ICCs ranged from 0.71 to 0.98. ER and IR ROM were 3-5 degrees greater for the digital level than the goniometer (p < 0.01). Goniometric vs. digital level LOA ranged from 6 degrees to 11 degrees for shoulder flexion. Both measurement techniques had excellent intratester reliability, but for intertester reliability ICCs were 20% lower and LOA were 2.3 times higher than intratester values. Reliability estimates were similar between the digital level and the goniometer. However, because glenohumeral rotation was 3-5 degrees greater for the digital level than the goniometer (systematic error), the two methods cannot be used interchangeably. On the basis of the average intratester LOA for the goniometer and the digital level, a change of 6-11 degrees is needed to be certain that true change has occurred. For comparison of measures made by two different therapists, a change is of 15 degrees is required to be certain a true change has occurred. A digital level can be used to reliably measure shoulder ROM but should not be used interchangeably with a standard goniometer.