Oxytocin is a hypothalamic neuropeptide with both centrally and peripherally directed pathways. Data from experimental animals indicate that oxytocin impairs consolidation of aversively conditioned behaviors and is released after feeding or experimental gastric distension. The authors report that the mean CSF oxytocin level of five underweight women with restricting anorexia, but not 12 underweight bulimic anorexic women or 35 normal-weight women with bulimia nervosa, was significantly lower than the level of 11 control subjects. Restricting anorexic patients' low CSF oxytocin levels may reflect their persistently low food intake, and this behavior may exacerbate their tendency for perseverative preoccupation with adverse consequences of food intake.