Many researchers wrongly assume that validity is the§property of an instrument, and that once validity has§been 'demonstrated' no further analysis is required§when it is used in a different research context.§This work challenges that idea and seeks to remind§researchers that validity, the 'ne plus ultra' of any§research, is a multi-layered process incorporating§both statistical and judgmental evidence, that must§be specifically accounted for in any empirical project.§A Japanese translation of Bennett and Hammer's§Intercultural Development Inventory (version 1) was§tested for content, concurrent, and consequential§validity following Messick's (1998) framework in§which these aspects of validity are seen to§contribute to an overarching judgment of construct§validity. The validation analysis raised questions§about whether results from a translated IDI, and by§extension the stages of the Developmental Model of§Intercultural Sensitivity (DMIS) upon which it is§based, are transferable across languages and cultures.§This work serves as a reminder that validity is a§critical element, and that it must be an explicitly§addressed, particularly in cross-cultural research.