Bulimia, a disorder of episodic binging and purging, remains without a known etiology. A case report is presented of a patient who attributed bulimic episodes to efforts at inducing euphoria. Experimental pain tolerance was increased by bulimic vomiting, blocked by naloxone, but not by saline. Vomiting was also associated with falls in depression and anxiety. Plasma ACTH and cortisol, putative markers for beta-endorphin, also rose following vomiting. It is hypothesized that in some bulimics, the disorder arises by virtue of an addiction to one's own internally released endogenous opioid peptides.