This chapter will address the many questions about primary anorexia nervosa (AN) that remain unanswered, with particular attention given to certain factual aspects of the syndrome that are well-established but unexplained. I shall refrain from mentioning the observations that have been made by psychiatric and psychoanalytic clinicians (1). These observations have led to concepts about the nature of the remorseless self-starvation, or the excessive control over eating, that are an important but not the invariant feature of the behavior of some patients with AN. Therefore, these concepts can only account for some aspects of the syndrome, and do not explain the fact that the syndrome begins with amenorrhea in about half the patients.