There are kinds of psychosis associated with a more benign clinical pattern than the major psychoses and these have been named atypical psychoses. The book concentrates on the findings of the course on Atypical or Transitory Psychoses held at UNED in Tudela in 2009, organized by the centre in collaboration with the Faculty of Psychology of UNED, the University of Cambridge (UK) and the Monterrey Institute of Technology (Mexico). This was sponsored by the Education Council of the Government of Navarre. The participants included experts from Mexico, the UK, Italy and Spain, from various universities (Cambridge, Modena, Bern, UNED, Autonoma de Barcelona, Complutense, Cordoba, Barcelona, Vigo and Technological Institute of Monterrey).