Self-mutilation, the deliberate destruction or alteration of body tissue without conscious suicidal intent, occurs in a variety of psychiatric disorders. Major self-mutilation includes eye enucleation and amputation of limbs or genitals. Minor self-mutilation includes self-cutting and self-bitting. The author examines patients' explanations for self-mutilation, which frequently focus on religious or sexual themes, and discusses scientific explanations that draw on biological, psychological, social, and cultural theories. Although no one approach adequately solves the riddle of such behaviors, habitual self-mutilation may best be thought of as a purposeful, if morbid, act of self-help.