Currently, in the UK military, and particularly in the Army, a significant number of personnel are regularly discharged on the grounds of being assessed as "Temperamentally Unsuitable (TU) for military duties", under Queen’s Regulations (QRs): (Army) 9.414 and 9.434 (1). In the last two years (2001-2003), preliminary figures suggest that approximately 700 serving personnel were recommended for discharge under this category by only four psychiatrists in the south of England. The regulations governing TU have been in existence and essentially unchanged since their development long before the 1960s albeit subject to parliamentary quinquennial review. The Army General and Administrative Instructions (AGAI) (2) standards also remain unchanged over this period. This paper raises questions about the current validity and relevance of existing TU concepts and regulations with suggestions as to what is being proposed in the context of changing roles, technology and advances in the modern armed forces.