Presence is one of the most important psychological constructs for understanding human-computer interaction. However, different terminology and operationalizations of presence across fields have plagued the comparability and generalizability of results across studies. Lee's (2004) unified understanding of presence as a multidimensional construct made up of physical, social, and self-presence, has created a unified theory of presence; nevertheless, there are still no psychometrically valid measurement instruments based on the theory. Two studies were conducted that describe the development of a standardized multidimensional measure of presence (the MPS) for a VR learning context based on this theory, and its validation using confirmatory factor analysis and item response theory. The results from Study 1 which included 161 medical students from Denmark indicated that the items used in the MPS measure a three dimensional theoretical model of presence: physical, social, and self-presence. Furthermore, IRT analyses indicated that it was possible to limit the number of items in the MPS to 15 (five items per sub-dimension) while maintaining the construct validity and reliability of the measure. The results of Study 2, which included 118 biology students from Scotland, supported the validity and generalizability of the MPS in a new context.