[Truncated abstract] Normal and pathological upper limb movement assessments rely on the valid and reliable identification of the glenohumeral joint centre of rotation (GHJ). However, clarifying the most suitable techniques to identify and reference this location has proved a challenge, and performing a variety of methods that lack validation is commonplace. This may not only be erroneous, but also prevents the standardised collection of upper limb biomechanical information. The principle aim of this research was to clarify the accuracy and reliability of various methods of GHJ identification, including both predictive and functional techniques, as well as the error associated with referencing the GHJ location during dynamic movement trials. Predictive methods of GHJ identification rely on a generic relationship between the GHJ position and predetermined anatomical distances or locations. The ISB recommended predictive method was developed and validated using cadavers, and it appears that a number of convenient, yet to be validated methods are routinely performed in preference of this recommended technique. In the present study, magnetic resonance imaging (MRI) was utilised to validate, in vivo, the accuracy of various predictive approaches; the ISB recommended method and a representative sample of commonly used techniques. A new multiple linear regression model and simple 3D offset method, were developed from the MRI identified locations of the GHJ and the surface markers. The results indicated that the new multiple linear regression model (13 ±4.6) mm and simple 3D offset (12 ±4.6 mm) found an average GHJ location closer to the MRI determined location than any of the established predictive methods (14-50 mm), including the ISB recommended method (32 ±8.2 mm), and a recently publicised amended 2nd version (16 ±8.4 mm). ... For instance when the optimal algorithm (geometric sphere fit), marker set and movement trial were used in the functional approach, average in vivo accuracy errors of 27 ±8.6 mm were reported, around half the error reported by the most accurate and reliable predictive method (13 ±4.6 mm). A further investigation aimed to determine the most suitable location to reference the GHJ during dynamic motion analysis trials. The GHJ was referenced in a number of upper arm and acromion technical coordinate systems (TCSs) in a series of static MRIs. This permitted the error associated with each set of markers to be calculated in vivo. The results indicated that a combination of TCSs defined from two sets of markers; one placed on the acromial plateau and one located proximally on the upper arm, produced the most accurate results, recording an average of 18 ±4 mm of error following a large humeral elevation (up to 180°). Furthermore, a distal upper arm set of markers proved to be inappropriate for GHJ referencing, reporting average errors greater than 30 cm in two large humeral elevations. Therefore, following the identification of the GHJ, its 3D location should be referenced in the average of two TCSs determined from respective sets of markers placed on the acromion and proximal upper arm, during dynamic trials.