This article describes the circumstances of the diagnosis of three of a group of 12 high-functioning multiple personality disorder patients. All had performed major social and professional activities with consistent competence, and all appeared to be neurotic patients suitable for classical psychoanalysis. All 12 had been misdiagnosed on at least three occasions before the correct diagnosis was made. Aspects of the difficulties encountered in assess these patients are discussed and guidelines for the preservation of their high level of function during the treatment process are offered.